Objective: Long-chain PUFA (LCPUFA) found in breast milk are derived from dietary sources and critical for optimal infant development. We examined associations between fish consumption and concentrations of LCPUFA and essential n-3 and n-6 fatty acids in breast milk among mothers living around Lake Victoria. Design: We used cross-sectional analyses of associations between recent fish consumption and breast-milk fatty acid concentrations. Setting: The study was conducted around Lake Victoria on Mfangano Island, Kenya, where multiple fish species are key dietary components and also are widely exported. Subjects: Breast-feeding mothers (n 60) provided breast-milk samples, anthropometric measurements and questionnaire responses. Results: In the previous 3 d, 97 % of women consumed a mean of 178 (sd 111) g fish (~2 servings/3 d). Mean breast-milk concentrations included DHA (0·75 % of total fatty acids), EPA (0·16 %), _-linolenic acid (ALA; 0·54 %), arachidonic acid (AA; 0·44 %) and linoleic acid (LA; 12·7 %). Breast-milk DHA concentrations exceeded the global average of 0·32 % in fifty-nine of sixty samples. We found native cichlids (Cichlidae) and dagaa (Rastrineobola argentea) contributed high levels of DHA, EPA and AA to local diets. We also found evidence for associations between fish species consumed and breast-milk LCPUFA concentrations when controlling for intake of other fish species, maternal body mass, maternal age, child age and exclusive breast-feeding. Conclusions: The fatty acid composition of breast milk was influenced by the fish species consumed. Ensuring access to diverse fish and particularly inexpensive, locally available species, may be important for diet quality as well as infant growth and development.