This study investigated the effect of level of Spirulina supplementation on the fatty acid (FA ) compositions of subcutaneous adipose, longissimus dorsi muscle, kidney, heart, and liver tissues in purebred and crossbred Australian Merino sheep. Forty-eight lambs sired by Black Suffolk, White Suffolk, Dorset and Merino rams were assigned into 4 treatment groups of daily Spirulina supplementation levels per lamb of 0 mL (control), 50 mL (low), 100 mL (medium) and 200 mL (high) referred to as 0, 5, 10 and 20% groups. The lambs were slaughtered after 9 weeks of supplementation and heart, kidney, adipose, liver and muscle tissue samples were collected. The results demonstrated significant variations in growth and body conformation traits and tissue and organ FA composition in response to the Spirulina supplementation. The medium-level Spirulina treatment group increased the ω-3 and ω-6 polyunsaturated fatty acid (PUFA ) composition in all tissues and organs significantly. The results suggest the use of medium level (100 mL/head/day) of Spirulina supplementation in order to increase lamb production with more ω-3 and ω-6 PUFA and therefore higher nutritional meat quality.