On his father's death, Pandulf was marginalised by his uncle, the reigning Pandulf Ironhead, who gave Capua and Benevento to his eldest son Landulf IV on his death in 981. That year, however, Landulf IV was forced to divide his principality for the first time since 910. Benevento was given to Pandulf. In May 987, he associated his son Landulf with him in the tradition of the Capuan dynasty begun by Atenulf I.
In 999, Otto III visited the shrine at the Sanctuary of Monte Sant'Angelo on Monte Gargano. On his return through Benevento, he signed a diploma in favour of the monastery of S. Sofia on 11 March. S. Sofia was the familial foundation of Pandulf's line and probably acted as their mausoleum. For reasons unknown, Otto and Pandulf had a falling out in 1000, possibly over the relics of Saint Bartholomew, patron saint of Benevento, to whom Otto had constructed a new church on the Isola Tiberina—San Bartolomeo all'Isola—just recently. According to the Annales Beneventani, Otto rex cum magno exercitu obsedit Benevento: "King Otto with a large army besieged Benevento." Nothing, however, came of it, except perhaps the yielding of certain relics (possibly the skin of Bartholomew).
Also in that millennial year, the Capuans ousted their imperialist prince, Adhemar, and invited Landulf di Sant'Agata, Pandulf's brother, to be their new prince. In 1003, a rebellion led by Adelfer, Count of Avellino, ousted Pandulf and his son from Benevento. The princes did not remain exiled for long, however. In 1005, we find them ruling from their capital again. The revolt was a bad sign, though. Civil unrest was rising in the principality.
In 1007, Landulf of Capua died and Pandulf succeeded him alongside his son, Pandulf II of Capua. In 1011, 1012, or 1013, Pandulf's eponymous grandson, Pandulf III, the son of Landulf, was associated with the rule of Benevento. Thereafter, Pandulf the elder recedes from the pages of history until his death is recorded in 1014.