Plastic debris in marine environments has emerged as a growing environmental concern, particularly in coastal zones where land-sea interactions intensify anthropogenic pressures. This study presents a comprehensive assessment of both macroplastic and microplastic pollution in beach sediments along the southern Atlantic coast of Morocco, from Aglou to Sidi Ifni. Six beaches, which represent the gradient of urbanization and human influence, were surveyed in the month of May 2025, through the collection of beach surface sediment samples to determine macroplastic particles as well as microplastic particle analysis. Standardized protocols were applied to quantify plastic abundance, identify morphological types, and characterize polymer composition. The results revealed that all sampled beaches were contaminated with plastic debris. Macroplastics were more abundant in touristic and semi-urban sites, with packaging waste, fishing-related items, and plastic fragments being the most dominant categories. The Clean Coast Index (CCI) classified most beaches as “dirty” or “moderately dirty.” Microplastic particles were detected in all sediment samples, with fibers accounting for 66% of the total, followed by fragments (22%) and films (12%). Polymers such as polyethylene and polypropylene were predominant, reflecting their widespread use and environmental persistence. Statistical analysis using Kruskal–Wallis and Mann–Whitney U tests showed no significant differences in microplastic abundance among sites, suggesting that coastal dynamics, sediment properties, and hydrodynamic transport may overshadow localized sources. This study provides critical baseline data on plastic pollution in Moroccan coastal ecosystems and highlights the urgent need for integrated management strategies to mitigate the growing threat of plastic waste in the marine environment.