The intensification of agriculture has led to the widespread use of chemical pesticides for the control of pests and diseases. However, it has been demonstrated that these pesticides can enter the animal body through a number of different pathways, with the potential to cause a range of health issues. Since mammals living in different environments (such as aquatic and terrestrial areas) exhibit similar physiological patterns and mechanisms of xenobiotic bioaccumulation, we extend the investigation of pesticide ecotoxicity in aquatic and semi-aquatic mammals to include both aquatic and terrestrial mammals. This chapter categorizes mammals as terrestrial, marine, domesticated and human in order to discuss the bioaccumulation, toxicity and ecological health effects of pesticides. Toxicity studies encompass not only acute effects but also chronic and long-term effects, with a particular focus on organ, reproductive health, teratogenic and carcinogenic effects. Furthermore, the utilization of pesticides has an impact on the surrounding environment, biodiversity and the stability of the food chain, which in turn threatens the overall ecological health and system stability. In conclusion, this chapter examines emerging areas of pesticide development, including innovative biopesticides, advanced application technologies and enhanced degradation methods, with the objective of minimizing the adverse impacts of pesticides from source to field.