Plastic products are widely used in various fields, and the discarded plastics in the environment can be degraded into microplastics (MPs) or even nanoplastics (NPs), which significantly increases the risk of organism exposure. MPs/NPs have been found in aquatic organisms, birds of prey, and even humans. The detection of plastic particles in biological samples is more complicated than that in environmental samples. Biological samples are mainly composed of various organic substances such as proteins and lipids, which makes the pretreatment process particularly critical. Effective detection and accurate quantification of MPs/NPs are crucial to health risk assessment. In this paper, the exposure levels and composition of MPs/NPs in different tissues and organs of the human body, aquatic organisms, and birds of prey were reviewed. The digestion of biological samples (acids, bases, enzymes, and hydrogen peroxide digestion protocols) and MPs/NPs identification methods (spectroscopy and chromatography) were compared and their advantages and disadvantages were assessed, providing a methodological basis for plastic exposure risk assessment and pollution control.