The green alga Bryopsis pennata Lamouroux, collected from the coast of Karachi, has been investigated for its sterol and fatty acid compositions. Four sterols and 19 fatty acids have been isolated from methanolic extract of this alga and identified by (1)H-NMR, El- & GC-MS techniques. The sterol having cholesta skeleton was found as major constituent (78.12%), while other three with ergosta skeleton occurred in traces (5-9%). Seven saturated fatty acids were present in greater quantity (72.58%) than 12 unsaturated ones (27.41%). The latter included 7 monoenoic, 2 dicnoic, 2 trienoic and 1 pentaenoic adds. Tricosanoic acid was found in the highest amount (30.24%), cyclopentenyl undecanoic and heneicosapentaenoic acids were the unique and rare fatty acids detected.