ABSTRACT. – A total of 2103 specimens of an alien species Paracerceis sculpta (Holmes, 1904) was collected between November 2016 and July 2017 in Tunis Southern Lagoon, brackish area located in northern eastern Tunisia. The species is a native from southern California and invaded the Mediterranean Sea during the late seventies. P. sculpta was found below stones covered by biofouling and empty tests of barnacles. From the three distinct sexually mature male morphs of P. sculpta, only the larger (alpha) was found, confirming the absence of the two smaller male morphs (beta and gamma) in an introduced population. Females reached size at first sexual maturity from 4 mm in length, the fecundity ranged from 5 to 14 eggs. The high densities and occurrence of all stages of development of the intertidal isopod Paracerceis sculpta in the Tunis southern lagoon, suggests that the species is established in its new environment