Seaweeds are considered as ecologically and biologically important component in the marine ecosystems. Seaweeds make a substantial contribution to marine primary production and provide habitat for near shore benthic communities. Present status of seaweed diversity and temporal variation in their abundance along Tuticorin coastal waters were investigated. Fortnightly seaweed sampling was conducted for the period of five months from July 2014 to November 2014. Seaweed showed significant variation in its abundance and ranged from minimum 248 numbers of seaweed during September month to 953 numbers during November. In total 86 seaweed species belonging to 14 orders, 22 family and 36 genera were recorded. Rhodophyceae represented as dominant seaweed phylum with 32 species belonging to 7 order, 11 family and 18 genera followed by Chlorophyceae (27 species belonging to 3 order, 7 family and10 genera) and Phaeophyceae (27 species belonging to 4 order, 4 family and 8 genera). Caulerpa and Ulvawere were dominant genera along the Tuticorin coast followed by Gracilaria, Sargassum and Padina. Temporal variability in various diversity indices were calculated by using PRIMER v6 software. The calculated value ranges of biodiversity indices were: Shannon–Wiener diversity (H’) ranged from 3.91 to 4.38, Margalef’s species richness (‘d’) was from 11.32 to 15.18, Pielou’s evenness (J’) was in the range of 0.9727 to 0.9858 and the Bray-Curtis similarity found maximum between July and August (89.92%) followed by August and November (88.11%). Higher values for biodiversity indices indicated healthy nature of seaweed ecosystem along Tuticorin coastal waters. Present research report can provide basic information for commercial exploitation of seaweed resources along Tuticorin coastal waters.