In the present regional monograph 3,431 specimens of Cerithiopsidae, a family of very small and minute sea snails, are analyzed. The material was collected during two expeditions by the MNHN in Papua New Guinea: Papua Niugini 2012 and Kavieng Lagoon 2014. A total of 184 different species was identified, 67 of which are new to science. For 117 species the distribution ranges are expanded. Fourteen genera of Cerithiopsidae are represented: Cerithiopsidella (2 species), Clathropsis (15), Granulopsis (2), Horologica (33), Joculator (76), Marshallopsis (11), Ondulopsis (2), Prolixodens (2), Retilaskeya (3), Seila (6), Specula (4), Sundaya (1), Synthopsis (23), and Tubercliopsis (4).