His mother was Yvantia. He co-reigned with his father, Landulf II, from 943, when his grandfather Landulf I died, and with his brother Landulf III from 959. Sometime about 955, Pope John XII led an army of Romans, Tuscans, and Spoletans against Landulf II and Pandulf, but Gisulf I of Salerno came to their rescue and no battle was given. The pope and Gisulf made a treaty at Terracina. Gisulf and Pandulf had a strong alliance after that.
In 961, Landulf II died and Pandulf and his brother became sole princes, though the elder Pandulf was by far the more domineering. The Chronicum Salernitanum affirms the co-regency, however, and the principle of the indivisibility of the united Capua-Benevento as declared by Atenulf I in 900, when it says Beneventanorum principatum eius filii Pandolfum et Landulfum bifarie regebant . . . communi indivisoque iure, that is "the Beneventan principality was reigned in jointly by Pandulf and Landulf under indivisible common jurisdiction." However, this system eventually collapsed and Pandulf ruled in Capua while Landulf ruled in Benevento.
Late in 965, a rebellion in Rome overthrew Pope John XIII, who was arrested and carted off to imprisonment in Campania. Whether he escaped or was released, he arrived in Capua not much later, seeking the protection of Pandulf, who gladly gave it. In return, and for the favour of the citizens, he erected Capua into an archdiocese and gave Pandulf's brother John the pallium. After ten months of exile, another revolt in Rome gave opportunity for return and Pandulf sent the pope back with a Capuan escort.
In 967, the Emperor Otto I came down to Rome and granted Pandulf the vacant Duchy of Spoleto of Camerino and charged him with prosecuting the war against the Byzantine Empire. Pandulf and Landulf took part in the campaign of 968, but Landulf retired in illness and died at Benevento leaving two sons: Pandulf and Landulf. The Chronicum says Pandulf tenuit principatum una cum suo germanus annos octo, that is, "held the principality solely with his brother for eight years." Then he cheated his nephews out of their patrimony, made himself sole prince, associated with him his own son Landulf, and rejoined the imperial campaign. In that year, Otto left the siege of Bari in the charge of Pandulf, but the Lombard was captured in the Battle of Bovino (969) by the Byzantines and jailed in Constantinople. In 970, during his absence, the Byzantines besieged Capua and Marinus II of Naples ravaged the countryside. He was released later in the deal in which the Byzantine emperor John Tzimisces gave Theophano in marriage to Otto's son Otto II. During his absence, the great principality had been administerd by Landulf I, Archbishop of Benevento, and the young Landulf, with help from his mother, Pandulf's wife, Aloara. Benevento had been made an archdiocese in 969.
In the 960s, Byzantium had been trying to supplant German influence in Salerno and to this end may have engineered the rebellion which temporarily unseated John XIII, a pro-German pope. Prince Gisulf of Salerno, however, was allied both to the Greeks and to his Lombard neighbour Pandulf, whom he had rescued some years before and who was, in fact, staunchly pro-German and anti-Greek. When Gisulf was deposed and removed from office by a religious insurrection led by his brother Landulf in 974, Pandulf restored him as his vassal. When Gisulf died childless in 977 or 978, Pandulf succeeded in Salerno as per their prior agreement. The policy of the Greeks was a thorough failure and Pandulf (and his Germans) was the winner in southern Italy. He had united all three of the Lombard principalities — Benevento, Capua, and Salerno — and had even gained Spoleto and Camerino. He ruled a large bloc of territories that stretched as far north as Tuscany and as far south as the Gulf of Taranto.
Pandulf's lands were partitioned among his sons, who fought endlessly over the inheritance. His son Landulf IV received Capua and Benevento and Pandulf II received Salerno. Otto II came down to Rome in 981, however, and Spoleto was given to Thrasimund IV, Duke of Camerino. Then, Pandulf's nephew Pandulf was given Benevento in a partition of Landulf's territory, in which Landulf kept Capua. Finally, Manso I of Amalfi dispossessed the younger Pandulf of Salerno and was confirmed by the Emperor.