The contaminationContamination ofHeavy metals freshwater ecosystems by pesticides and heavy metalsHeavy metals poses a significant threat to both environmentalEnvironmental and human health due to their persistence, tendency to bioaccumulate, and toxic effects. Traditional analytical methods for detecting these pollutantsPollutants, such as chromatography and atomic absorption spectroscopy, are precise but often require advanced equipment, skilled personnel, and long processing times. In response, biosensorsBiosensor have become promising tools for quick, sensitive, and on-site monitoringMonitoring of contaminants in aquaticAquatic environments. This chapter discusses recent advancements in biosensorBiosensor technologiesTechnology designed to detect pesticides and heavy metalsHeavy metals in freshwater systems. It covers how they work, the types of biorecognition elementsBiorecognition elements used (e.g., enzymesEnzymes, antibodiesAntibodies, whole cells, nucleic acids), and the transduction mechanisms (electrochemical, optical, piezoelectric). The chapter features essential examples of biosensorsBiosensor used with real freshwater samples, evaluates their performance in terms of sensitivity, selectivity, and detection limitsDetection limits, and discusses challengesChallenges such as matrix effects, sensor stability, and field deployment. Additionally, it explores future directions, including the use of nanomaterials, microfluidics, and wireless data transmission to improve biosensorBiosensor capabilities. By providing a thorough overview of current strengths and limitations, this chapter highlights the transformative potential of biosensorsBiosensor in protecting freshwater quality through the timely and effective detection of pollutantsPollutants.