The marine malacofauna of the Lamu Archipelago in Northern Kenya was studied in 2001. In this paper, known data from Spry (1964, 1968), Sawyer (1999, 2000), Wronski (2007) and Rosenberg et al. (2004) are supplemented by the results of the author’s fieldwork. A total of 55 gastropod and bivalve species was recorded; of which 23 are reported from Zanzibar but not listed in the East Africa section of the OBIS Indo-Pacific Molluscan Database. Five species (Pseudominolia climacota (Melvill, 1897); Terebra nassoides Hinds, 1844; Pupa cf solidula (Linne, 1758); Ostrea (Nanostrea) deformis Lamarck, 1819; Divaricella irplex (E.A. Smith, 1885)) were neither reported from Zanzibar nor listed by Rosenberg et al. (2004), and are therefore considered new for East Africa. The study represents the first comprehensive species list of marine gastropods and bivalves found in the tidal flats and beaches of the Lamu Archipelago.