A total of sixtynine foraminifera1 species belonging to 27 genera and 19 families have been identified from the sediment samples of the Chilka lake collected during three faunal surveys representing different seasons. Miliammina fusca, Ammobaculites exiguus, Ammonia beccarii (Linn6) and A. tepida are the most abundant species in the fauna. A study of biofacies shows that the fauna is characterized by Miliammina in the inner lagoon facies and by Ammonia beccarii (Linn 6) in the outer lagoon/channel facies. During premonsoon season, higher concentrations of total populations of Foraminifera and number of species have been observed due to its marine influence. Further, the fauna is a mixed assemblage due to incursion of the nearshore foraminiferids into it through the inlet by tidal currents. Faunal diversity, in general, increases seaward from the northern sector to the outer channel. Distribution patterns of Foraminifera are delineated, particularly in relation to their ecology. The fauna of the Chilka lake has been compared with that of certain Indian and overseas estuaries and most of the species reported in this paper are also known from the Indo-Pacific faunal province.