He was on intimate terms with the famous courtesan Gnathaena (Athenaeus xiii. pp. 579, 583). He is said to have written 100 comedies, the titles of fifty of which are preserved. He sometimes acted himself. To judge from the imitations of Plautus (Casina from the Κληρούμενοι, Asinaria from the Ὀναγός, Rudens from some other play), he was very skilful in the construction of his plots. Terence also tells us that he introduced into the Adelphi (ii. I) a scene from the Συναποθνήσκοντες, which had been omitted by Plautus in his adaptation (Commorientes) of the same play.
The style of Diphilus was simple and natural, and his language on the whole good Attic; he paid great attention to versification, and was supposed to have invented a peculiar kind of metre. The ancients were undecided whether to class him among the writers of the New or Middle comedy. In his fondness for mythological subjects (Hercules, Theseus) and his introduction on the stage (by a bold anachronism) of the poets Archilochus and Hipponax as rivals of Sappho, he approximates to the spirit of the latter.
Fragments in R. Kassel-C. Austin, "Poetae Comici Graeci" (PCG) vol. 5 (previously in T. Kock, Comicorum Atticorum fragmenta ii; see J. Denis, La Comédie grecque (1886), ii. p. 414; R.W. Bond in "Classical Review" 24/1 (Feb. 1910) with trans. of Emporos fragm.).