In the present study, a total of 2,333 specimens including both live and dead shells were collected from different parts of the Pennera River Estuary, Nellore, Andhra Pradesh, India, during 2011-2013. Sampling sites covered six different locations in the upper and middle reaches, the Palipalam canal, and the open mouth areas of the estuary. A total of 147 species of molluscs from 1,540 specimens were identified under two classes, 22 orders, 59 families, and 106 genera. Out of the 147 mollusc species, 63 species from 793 specimens belonged to Gastropoda, coming under nine orders, 32 families, and 49 genera. A further 84 species of bivalves were identified, belonging to 13 orders, 27 families, and 57 genera. This is the first comprehensive report on the molluscan fauna of the Pennera estuary and complements other work done in various other estuaries around the country by different researchers.