Seasonal diversity and distribution of seven benthic foraminiferal species belonging to six families in association with the marine sponge Liosina paradoxa attached to pneumatophores of the mangrove Avicennia marina were documented at four sampling stations (St1–St4), Sandspit backwaters, Karachi coast during 2013. The calcareous species Ammonia sp. and Quinqueloculina laevigata were recorded at all stations in different seasons whereas the agglutinated species Ammotium cassis and Rotaliammina squamiformis were the most dominant species throughout the study. During the study period, water temperature ranged between 22.5–30.3°C, salinity ranged from 35–40, dissolved oxygen ranged from 0.11–3.45 mg L−1, and pH ranged from 7.15–7.69. The maximum relative abundance (45.65%) of foraminiferal species occurred at St2 from an exposed area while minimum relative abundances (13.04%) were recorded at St3 in sheltered areas. A K-dominance curve showed that highest frequency values in species were observed in the post-monsoon season as compared to the monsoon season. The present study is the first to report the foraminiferal assemblages associated with a marine sponge (Liosina paradoxa) from the mangrove habitat at Sandspit backwaters, Karachi.