The effect of various plant growth regulators (6-benzylaminopurine (BAP), 6-furfurylaminopurine (Kinetin), gibberellic acid (GA3), 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA)) on the yields of biomass and an essential free fatty acid (alpha-linolenic acid from Chlorella pyrenoidosa) were studied.NAA and BAP showed significant increase of 2.2- (0.2905 to 0.6497 g/L) and 1.26-fold (0.2905 to 0.3727 g/L) in biomass yield, respectively. The only plant growth regulators belonging to the group cytokinins (BAP and kinetin) showed prominent rise in the yields of alpha-linolenic acid. BAP and kinetin resulted in 2.94- (371.83 to 1105.93 lg/mL) and 3.03-fold (371.83 to 1128.25 lg/mL) increase in ala yields, respectively, compared with that of control.