Although macrobenthic assemblages are considered as major players in many ecosystems around the world, the ecology of Caspian Sea macrobenthos is currently understudied. This study describes the species composition and quantitative distribution of macrobenthos in the southern Caspian Sea and relates the distribution to seasonal changes at three depths (1, 5 and 10 meters) on the Boojagh Marine National Park (BMNP) coast in the southern Caspian Sea between the summers of 2015 and 2016. To investigate the distribution of macrobenthos in BMNP, the data of 450 samples were analyzed. In this study sixteen species were identified: Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carausui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Nais sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor, Amphibalanus improvisus. Among them, the non-indigenous C. glaucum was the dominant species, accounting for 27% of the total abundance and in descending order P. grimmi with 14. 4%, A. improvisus with 8. 7%, M. lineatus with 7. 9%, Nais sp. with 7. 5%, N. carausui with 5. 2%, P. motasi with 5%, S. gynobranchiata with 4. 5%, H. invalida with 5%, M. Caspica with 3. 1%, P. sowinskyi with 2. 5%, O. caspius with 2. 4%, A. kolesnikovi and H. diversicolor with 1. 8%, S. gracilis with 1. 6% and P. pectinatum with 1. 5% were in the next rank. Significant differences in abundance across the sixteen species were observed among depths and seasons. This study highlights the potential consequences of established non-indigenous species in the southern Caspian Sea.