Two new allocreadiid trematodes are described from the intestine of characid fishes from Rio Itaya, a tributary of the Amazon River near Iquitos, Peru. Auriculostoma foliaceum n. sp. is described from Bryconops cf. caudomaculatus (Günther, 1864) Backup, 2003, and Auriculostoma diagonale n. sp. from Stethaprion cf. erythrops Cope, 1870. Auriculostoma foliaceum n. sp. differs from its congeners by having a foliated lateral margin and lacking vitelline follicles in the forebody. Auriculostoma diagonale n. sp. differs from all of its congeners except Auriculostoma platense (Szidat, 1954) Scholz, Aguirre-Macedo, and Choudhury, 2004, by having oblique rather than tandem testes and differs from A. platense by having a much more elongated cirrus sac. Phylogenetic hypotheses based on analyses of 3 alignments of partial sequences of the 28S rDNA gene conducted in this study provide a framework for revaluating the classification of Allocreadiidae Looss, 1902. The present analyses show that (1) Paracreptotrematina limi Amin and Myer, 1982, does not belong in the Allocreadiidae; (2) Creptotrematina aguirrepequenoi Jiménez-Guzmán, 1973 (spelled here without diacritic mark), does not belong to Paracreptotrematina Amin and Myer, 1982, but remains in the Allocreadiidae; (3) Auriculostoma astyanace Scholz, Aguirre-Macedo, and Choudhury, 2004, is closely related to C. aguirrepequenoi and Wallinia chavarriae Choudhury, Hartvigsen-Daverdin, and Brooks, 2002; (4) Megalogonia Surber, 1928, is retained as an accepted genus in the Allocreadiidae; and (5) Margotrema Lamothe-Argumedo, 1970, is found to be nested among 3 species of Crepidostomum Braun, 1900.