His father died when he was two years old and he remained under the guardianship of his cousin, Guillaume Jourdain, count of Cerdagne (d. 1109), until he was five. He was then taken to Europe and his brother Bertrand gave him the county of Rouergue. In his tenth year, upon Bertrand's death (1112), he succeeded to the county of Toulouse and marquisate of Provence, but Toulouse was taken from him by William IX, count of Poitiers, in 1114, who claimed it by right of his wife Philippa of Toulouse, daughter of William IV of Toulouse. He recovered a part in 1119, but continued to fight for his possessions until about 1123. When at last successful, he was excommunicated by Pope Callixtus II for having expelled the monks of Saint-Gilles, who had aided his enemies.
He next fought for the sovereignty of Provence against Raymond Berenger III, and not till September 1125 did the war end in an amicable agreement. Under it Jourdain became absolute master of the regions lying between the Pyrenees and the Alps, Auvergne and the sea. His ascendancy was an unmixed good to the country, for during a period of fourteen years art and industry flourished. About 1134 he seized the viscounty of Narbonne, only restoring it to the Viscountess Ermengarde (d. 1197) in 1143. The claim of the now deceased Philippa of Toulouse was pressed again when Louis VII besieged Toulouse in 1141, in right of his wife Eleanor of Aquitaine, the granddaughter of Philippa, but without result.
Next year Jourdain again incurred the displeasure of the church by siding with the rebels of Montpellier against their lord. A second time he was excommunicated; but in 1146 he took the cross at the meeting of Vezelay called by Louis VII, and in August, 1147 embarked for the East in the Second Crusade. He lingered on the way in Italy and probably in Constantinople. Alphonse might have met Eastern Roman Emperor Manuel I Comnenus during his visit there.
But in 1148 Alphonse had finally arrived at Acre. Among his companions he had made enemies and he was destined to take no share in the crusade he had joined. He was poisoned at Caesarea, either by Eleanor of Aquitaine, the wife of Louis, or Melisende, the mother of Baldwin III, king of Jerusalem suggesting the draught.