Fisheries discards in the Moroccan Mediterranean Sea present a significant challenge at the intersection of marine resource management and societal concerns. Bottom trawl fisheries, which involve dragging nets along the seabed, capture a wide array of marine species, many of which are subsequently discarded. This study offers the first comprehensive analysis of discard composition from Moroccan trawl fleets, drawing on data collected from 2019 to 2022 through an onboard sampling program. Among the 103 species from 59 families discarded, 16 were elasmobranchs and 88 were bony fishes. Discarded biomass showed significant variation based on season, fishing areas, and their interaction, with discard ratios ranging from 1.06% to 43.7%. Teleostei made up the predominant fraction of discarded biomass, followed by Elasmobranchii, Thaliacea, and Holocephali. The study found significant variations in mean biomass values across different ports and seasons, highlighting dynamic patterns in biomass distribution among marine classes. However, the number of species recorded in discards remained stable across ports and seasons, indicating consistent environmental conditions. The findings underscore the need for targeted fishery management measures to minimize the ecological impacts of discards, tailored to specific times and locations.