Research on microplastic pollution and its effects on atmospheric, aquatic, and terrestrial environments has grown rapidly as potential risks for human health are recognized. Recently, microplastic particles have been detected in a variety of human tissue samples (e.g., blood, placenta, lung tissue), but studies use different methods of collection, preparation, and analysis, making results difficult to compare. In particular, the risk of microplastic contamination during sample collection is high and can potentially produce misleading results. Here we present a set of guidelines to mitigate all sources of potential plastic contamination while collecting cadaveric tissue samples. We discuss specific protocols for the collection of three tissue types: (1) internal body fluids; (2) soft tissue; and (3) tissue lining body orifices. Guidelines for each tissue type include sterilization of equipment and specimen, extraction of the sample, and containment of the cadaveric specimen after removal. Each methodology has the potential to be modified to collect samples from any anatomical region within the human body. Representatives from each tissue type (intestinal contents, lung tissue, and contents from the nasal cavity) are presented.