<p>This study provides a comprehensive spatial and seasonal assessment of environmental quality in the Porto Novi coastal zone (Boka Kotorska Bay, Adriatic Sea), focusing on the distribution of phytoplankton, nutrients, and fecal bacteria in water and sediment. Sampling was conducted at six stations over four seasons during 2019–2020. The PN1 station consistently showed the highest levels of fecal bacteria, particularly in spring, while sediments acted as a reservoir for fecal bacteria, especially at PN1 and PN3 during spring and autumn. Diatoms were the dominant phytoplankton assemblage with maximum abundance in spring and summer, while dinoflagellates reached the highest abundance in autumn. Coccolithophores had bimodal growth peaks: in spring and autumn, especially in lower layers. Total phytoplankton abundance bloom was the most intensive in summer, at the PN1 location. The Integrated Parameter Response (IPR) index indicated elevated ecological pressure in summer and autumn, while PCA analysis separated PN1, PN2, and PN3 locations as well as spring and winter seasons. Physicochemical parameters (except nitrite) and fecal bacteria remain within threshold limits, but a higher prevalence of fecal bacteria in sediment, intense phytoplankton blooms reaching up to 10⁵ cells L⁻¹, the presence of potentially toxic phytoplankton species, and seasonal nutrient enrichment patterns, suggest latent pollution and pressure from land-based sources. This research highlights the need for further seasonal monitoring and serves as a baseline to make strategies for decision-makers.</p>