Algae play a crucial role in aquatic ecosystems by producing oxygen and forming the base of the food chain. Contaminants such as industrial chemicals, pharmaceuticals, pesticides, heavy metals, and synthetic nano/microparticles can cause adverse responses in algae, disrupting the balance of aquatic ecosystems. This review discusses the ecotoxicological responses of algae to contaminants in aquatic environments, highlighting key points: (1) Polycyclic aromatic hydrocarbons accumulate in food chains and ecosystems, posing a major environmental health concern. (2) Bisphenol A negatively affects algae by inhibiting biochemical and physiological processes, with half maximal effective concentrations ranging from 1.0 mg/L to 100 mg/L. (3) Per- and polyfluoroalkyl substances, though present in low concentrations, can cause significant toxic effects when combined with other contaminants. (4) An exposure level of 1000 ng/L is unsafe for ecosystems, leading to algal growth inhibition, including damage to photosynthesis and DNA replication. (5) Chemical, biological, and physical factors influence the ecotoxicity of chemicals to algae, creating complex effects at the community level. (6) Monitoring and strategic interventions are essential to protect the sustainability of aquatic ecosystems. Environmental stressors, such as pollutants and changes in land use, contribute to biodiversity loss and ecosystem degradation. Harmful algal blooms damage marine ecosystems and human health. Agricultural activities and high cadmium levels negatively affect aquatic biota. The review emphasizes the importance of understanding the ecotoxicological responses of algae to contaminants, highlighting the need for monitoring and intervention to ensure the sustainability of aquatic ecosystems.Algae play a crucial role in aquatic ecosystems by producing oxygen and forming the base of the food chain. Contaminants such as industrial chemicals, pharmaceuticals, pesticides, heavy metals, and synthetic nano/microparticles can cause adverse responses in algae, disrupting the balance of aquatic ecosystems. This review discusses the ecotoxicological responses of algae to contaminants in aquatic environments, highlighting key points: (1) Polycyclic aromatic hydrocarbons accumulate in food chains and ecosystems, posing a major environmental health concern. (2) Bisphenol A negatively affects algae by inhibiting biochemical and physiological processes, with half maximal effective concentrations ranging from 1.0 mg/L to 100 mg/L. (3) Per- and polyfluoroalkyl substances, though present in low concentrations, can cause significant toxic effects when combined with other contaminants. (4) An exposure level of 1000 ng/L is unsafe for ecosystems, leading to algal growth inhibition, including damage to photosynthesis and DNA replication. (5) Chemical, biological, and physical factors influence the ecotoxicity of chemicals to algae, creating complex effects at the community level. (6) Monitoring and strategic interventions are essential to protect the sustainability of aquatic ecosystems. Environmental stressors, such as pollutants and changes in land use, contribute to biodiversity loss and ecosystem degradation. Harmful algal blooms damage marine ecosystems and human health. Agricultural activities and high cadmium levels negatively affect aquatic biota. The review emphasizes the importance of understanding the ecotoxicological responses of algae to contaminants, highlighting the need for monitoring and intervention to ensure the sustainability of aquatic ecosystems.