The desert locust Schistocerca gregaria is a destructive pest for several crops, particularly which are considered as the main food sources for human and animals. Much attention has been paid to use the plant extracts or plant products for controlling this pest. The present study aimed to investigate the disturbing effect of Nimbecidine on the phosphatase activity in S. gregaria. The penultimate instar nymphs were treated, through the fresh food, with 1.0 and 0.3% Nimbecidine and the activities of acid phosphatase (ACP) and alkaline phosphatase (ALP) were estimated in the last instar nymphs and adults. The most important results could be summarized as follows. Nimbecidine significantly promoted the ACP activity in haemolymph, irrespective of the stage, age, or concentration. In addition, Nimbecidine exhibited a remarkable inducing effect on the enzyme activity in fat bodies, regardless the stage and age, with an exception of the late-aged nymphs in which the enzyme activity was suppressed. Regarding the effect of Nimbecidine on ALP activity in haemolymph of the nymphs and adults, results clearly displayed a general reducing effect of Nimbecidine on the enzyme activity in haemolymph of the last nymphal instar. An exceptional case of promoting action was detected in the newly emerged adults, at the higher concentration. In respect of the effect on ALP activity in fat bodies, results indicated that the enzyme activity was significantly induced in nymphs but reduced in adults.