This article will explore Jerome's understanding of sinlessness and will argue that he saw himself just as opposed to Augustine as to Pelagius. I begin by exposing Jerome's context in the Pelagian Controversy. I then expose his understanding of sinlessness. Next, I turn to his arguments in Ep. 133 and the first two books of his Dialogi contra Pelagianos. In book three of that text, we notice a change in his arguments which indicates that Jerome is no longer arguing only against Pelagius; he now disagrees with Augustine as well. I then examine a variety of issues besides sinlessness in the third book of the Dialogi that reveal that Jerome disagreed with Augustine on multiple topics, showing that his opposition to Augustine's position on sinlessness was not exceptional. Finally I turn to statements by Jerome that seem to indicate a positive appreciation for the Bishop of Hippo, but which on closer inspection are seen to contain latent criticisms.