His Glasgow connections and political profile were already well-established enough that in 1174 Jocelin succeeded Enguerrand as Glasgow's bishop. As Bishop of Glasgow, he was a royal official. In this capacity he travelled abroad on several occasions, and performed the marriage ceremony between King William the Lion and Ermengarde de Beaumont, later baptising their son, the future King Alexander II. Among other things, he has been credited by modern historians as "the founder of the burgh of Glasgow and initiator of the Glasgow fair", as well as being one of the greatest literary patrons in medieval Scotland, commissioning the Life of St Waltheof, the Life of St Kentigern and the Chronicle of Melrose.
Like that of almost every character from this period, Jocelin's year of birth is unknown to modern historians. It is known that he entered as a novice monk in Melrose Abbey during the abbacy of Waltheof (ab. 1148–1159), and from documentary evidence it seems likely that Jocelin entered Melrose about 50 years before his death in 1199. As the rules of the Cistercian order prevented entry as a novice before the age of 15, it is likely that he was born around the year 1134. Little is known about Jocelin's early life or his early career as a Melrose monk. He obviously successfully completed his one-year noviciate, the year in which a prospective monk was introduced to monasticism and judged fit or unfit for admittance. We know that Abbot Waltheof (Waldef) thought highly of him and granted him many responsibilities. After the death of Abbot Waltheof, his successor, Abbot William, refused to encourage the rumours which had quickly been spreading about Waltheof's saintliness. Abbot William attempted to silence such rumours, and shelter his monks from the intrusiveness of would-be pilgrims. However, William was unable to get the better of Waltheof's emerging cult, and his actions had alienated him from the brethren. As a result, William resigned the abbacy in April 1170. Jocelin was by this stage the Prior of Melrose, that is, the second in command at the monastery, and thus William's most likely replacement.
So it was that Prior Jocelin became abbot on 22 April 1170. Jocelin embraced the cult without hesitation. Under the year of his accession, it was reported in the Chronicle of Melrose that:
The tomb of our pious father, sir Waltheof, the second abbot of Melrose, was opened by Enguerrand, of good memory, the bishop of Glasgow, and by four abbots called in for this purpose; and his body was found entire, and his vestments intact, in the twelfth year from his death, on the eleventh day before the Kalends of June [22 May]. And after the holy celebration of mass, the same bishop, and the abbots whose number we have mentioned above, placed over the remains of his most holy body a new stone of polished marble. And there was great gladness; those who were present exclaiming together, and saying that truly this was a man of God ...Promoting saints was something Jocelin would repeat at Glasgow, where he "transferred his enthusiasm to St Kentigern and commissioned a hagiography of that saint, the saint most venerated by the Celts of the diocese of Glasgow. It is no coincidence that Jocelin of Furness, the man who wrote the Life of St. Waltheof, was the same man later commissioned to write the Life of St. Kentigern.
This kind of literary patronage started while Jocelin was abbot of Melrose. Archie Duncan has shown that it was probably Jocelin who first commissioned the writing of the Chronicle of Melrose. Duncan argued that Jocelin commissioned the entries dealing with the period between 731 and 1170, putting the writing in the hands of a monk named Reinald (who would later become Bishop of Ross). This chronicle is one of the few extant chronicles from "Scotland" in this period. G. W. S. Barrow, writing before Duncan advanced these arguments, noted that down to the end of King William's reign "the chronicle of Melrose Abbey ... represents a strongly 'Anglo-Norman' as opposed to a native Scottish point of view". It is thus possible that this anti-Scottish world-view reflected that of Jocelin's, at least before he left the abbey.
After his election to the prestigious bishopric of Glasgow in 1174, Jocelin would continue exerting influence on his home monastery. Jocelin brought one of his monks from the abbey, a man called Michael, who acted as Jocelin's chaplain while Bishop of Glasgow. He did not resign his position as abbot until after his consecration in 1175. Jocelin consecrated his successors as abbot, and continued to spend a great deal of time there. Moreover, he used his position as bishop to offer the monastery patronage and protection.
He was soon faced with a political challenge to the independence of his church. The challenge came from the English church, and was not new, but had lain dormant for some decades. The reason it was awakened was that in the summer of 1174 King William had invaded northern England, and on 13 July, having been caught underprotected during a siege at Alnwick, was captured and taken into English custody. The capture was disastrous for the king, leading to a revolt by Gilla Brigte, Lord of Galloway, and to many of William's discontented subjects "ruthlessly" slaying "their English and French neighbours" and perpetrating a "most wretched and widespread persecution of the English both in Scotland and Galloway", that is, of the English and French-speaking settlers William and his predecessors had planted around the castles and towns of his Gaelic-speaking territories in order to increase royal authority. Worse still, and more significantly for Jocelin, in the following year King Henry II of England forced William to sign the Treaty of Falaise, a treaty which made William Henry's vassal specifically for Scotland and sanctioned the subordination of the kingdom's bishoprics to the English church.
Jocelin did not, in the end, submit either to the Archbishop of York or even the Archbishop of Canterbury and managed to obtain a Papal Bull which declared the see of Glasgow to be a "special daughter" of the Roman Patriarchate. Jocelin, moreover, does not seem to have been interested in the independence of the other "Scottish" sees, but merely to maintain his own episcopal independence, i.e. that of the bishopric of Glasgow. On 10 August 1175, along with many other Scottish-based magnates and prelates, Jocelin was at Henry's court giving his obedience to the king as stipulated in the treaty. Jocelin again appeared at King Henry's court in January 1176. This time church matters were on the agenda. When the Archbishop of York confronted Jocelin over the subordination of the bishopric of Glasgow to the archbishopric of York, Jocelin refused to acknowledge this part of the treaty, and presented him with the Papal Bull declaring Glasgow to be a "special daughter".
This Bull was confirmed by Pope Alexander's successor Pope Lucius III. Jocelin had obtained this confirmation while at Rome in late 1181 and early 1182. He had been sent there by King William, along with abbots of Melrose, Dunfermline and Kelso and the prior of Inchcolm, in order to appeal to the Pope regarding his stance in a struggle over the Bishopric of St Andrews and the sentence of excommunication and interdict the Pope had placed over the king and kingdom. The dispute concerned the election to the bishopric of John the Scot, which had been opposed by the king, who organised the election of his own candidate, Hugh. The mission was successful. The Pope lifted the interdict, absolved the king and appointed two legates to investigate the issue of the St Andrews succession. The Pope even sent the king a Golden Rose, an item usually given to the Prefect of Rome. The issue of the succession, however, did not go away. In 1186, Jocelin, along with the abbots of Melrose, Dunfermline and Newbattle, excommunicated Hugh on the instructions of Pope Lucius. Hugh travelled to Rome in 1188, and obtained absolution, but he died of the pestilence in that city a few days later, thus allowing the issue to be resolved.
It is certainly obvious that Jocelin was one of the most respected figures in the kingdom. In this era, the Pope appointed Jocelin Judge-delegate (of the Papacy) more times than any other cleric in the kingdom. As a bishop and an ex-abbot, various bishoprics and monasteries called him in to mediate disputes, as evidenced by his frequent appearance as a witness in dispute settlements, such as the dispute between Arbroath Abbey and the Bishopric of St Andrews, and a dispute between Jedburgh Abbey and Dryburgh Abbey. Jocelin had the respect of the secular elite too. He witnessed 24 royal charters and 40 non-royal charters, including charters issued by David, Earl of Huntingdon (the brother of King William), Donnchadh, Earl of Carrick, and Alan Fitzwalter, High Steward of Scotland. Jocelin had been with King William when he visited the English court in 1186, and again accompanied the king to England when the king travelled to Woodstock near Oxford to marry Ermengarde de Beaumont on 5 September 1186. The marriage was blessed by Bishop Jocelin in their chamber, and it was to Jocelin's escort that King William entrusted her for the journey to Scotland. When a son was born to William and Ermengarde, the future King Alexander II, it was Jocelin who performed the baptism. In April 1194, Jocelin again travelled to England in King William's company when William was visiting King Richard I. Jocelin's intimacy with the king would be the key to earning his patronage, thus making possible the legacy that Jocelin would leave to Glasgow.
His years at Glasgow left a mark on history that can be compared favourably with any previous or future bishop. Jocelin commissioned his namesake Jocelin of Furness, the same man who had written the Life of St. Waltheof, to write a Life of St. Kentigern, a task all the more necessary because, after 1159, the Papacy claimed the right to canonise saints. Kentigern, or Mungo as he is popularly known, was the saint traditionally associated with the see of Glasgow, and his status therefore reflected on Glasgow as a church and cult-centre. There had already been a cathedral at Glasgow before Jocelin's episcopate. The idea that the ecclesiastical establishment before Jocelin was simply a small church with a larger Gaelic or British monastic establishment has been discredited by scholars. Jocelin did, though, expand the cathedral significantly. As the Chronicle of Melrose reports for 1181, Jocelin "gloriously enlarged the church of St Kentigern". However, more work was created for the builders when, sometime between the years 1189 and 1195, there was a fire at the cathedral. Jocelin thus had to commission another rebuilding effort. The new cathedral was dedicated, according to the Chronicle of Melrose, on July 6, 1197. It was built in the Romanesque manner, and although little survives of it today, it is thought to have been influenced by the cathedral of Lund, the archbishop of which had consecrated Jocelin as bishop.
However, he left a still greater legacy to the city of Glasgow. At some point between the years 1175 and 1178, Jocelin obtained from King William a grant of burghal status for the settlement of Glasgow, with a market every Thursday. The grant of a market was the first ever official grant of a weekly market to a burgh. Moreover, between 1189 and 1195, King William granted the burgh an annual fair, a fair still in existence today, increasing Glasgow's status as an important settlement. As well as new revenues for the bishop, the rights entailed by Glasgow's new burghal status and market privileges brought new people to the settlement, one of the first of whom was one Ranulf de Haddington, a former burghess of Haddington. The new settlement was laid out (probably under the influence of the burgh of Haddington) around Glasgow Cross, down the hill from the cathedral and old fort of Glasgow, but above the flood level of the River Clyde.
When Jocelin died, he was back at Melrose Abbey, where his career had begun. He may have retired to Melrose knowing his death was near. Jocelin certainly did die at Melrose, passing away on St Patrick's Day (March 17), 1199. He was buried in the monks' choir of Melrose Abbey Church. Hugh de Roxburgh, Chancellor of Scotland, was elected as Jocelin's replacement. The Chronicle of Melrose has only a short obituary.