Pammachius was one of several people who denounced Jovinian, who was later condemned at a synod in Rome, to Pope St. Siricius. This denunciation caused St. Jerome to write his own criticism of Jovinian's teachings, however, Pammachius criticized this work "for prudential reasons." This led to a correspondence between the friends, in which Jerome thanked his friend but defended his work.
After Paulina's death in 397, Pammachius devoted his life to prayer and works of charity. With the help of St. Fabiola, Pammachius built a hospice for the poor at Porto.
He continued his correspondence with St. Jerome, urging him to translate Origen's "De Principiis." Pammachius also condemned the Donatist heresy and exhorted the people of Numidia to abandon it, for which action he received a letter of thanks from St. Augustine.
Pammachius died in Rome in the year 409.