As massive anthropogenic plastic wastes are released into the environment, micro/nanoplastics (MNPs) may be accumulated in various animals and lead to a variety of negative effects, which impact their health and growth. In this review, we summarized the studies related to toxicity of MNPs in animals and their toxicological mechanisms, and comprehensively reviewed the negative effects of MNPs on various animal organs and the signaling pathways. Additionally, we summarized current research on various possible strategies for alleviating the toxicity of MNPs, including probiotics, vitamins, and other organic compounds. This review aimed to appeal for more in-depth exploration of novel and convenient detoxification methods to effectively alleviate the toxicity of MNPs in animals, which helps protect animals from the adverse effects of MNPs, and provides new ideas and relevant recommendations for future research directions.