Phycocyanin, a blue colorant from the cyanobacterium (blue green alga) Spirulina platensis was evaluated for its safety as a natural food colour by toxicity evaluation studies in albino rats. Acute and subchronic studies on phycocyanin were conducted on both sexes of albino rats. Phycocyanin at high concentrations‐ 0.25 to 5.0 g/kg body weight (w/w) did not induce any symptoms of toxicity nor mortality of the animals. Feeding of low concentrations of phycocyanin at 0.5 to 4.0 g/kg in the diet for 14 weeks did not affect food intake or body weight gain of phycocyanin‐fed rats compared to control animals. Terminal values on absolute and relative weights of vital organs, hematology and serum enzymes did not reveal any differences between phycocyanin‐fed and control groups. Histological examination of vital organs did not show any remarkable differences between treated and control groups. Overall, consumption of phycocyanin, a natural colorant from Spirulina platensis did not result in adverse effects in experimental animals.