Identifying and characterizing microplastics in wastewater requires powerful analytical methods that can address the diverse sizes, shapes, and polymer compositions of these plastics. This chapter provides an in-depth overview of the most common analytical approaches to studying microplastics, with a particular focus on their use in complex wastewater and sludge matrices. Although the limitations of polymer identification are considered, microscopic methods, including optical, scanning electron, and fluorescence microscopy, are highlighted as essential tools for observing and quantifying particles across different size scales. Spectroscopic methods, in particular Fourier-transform infrared (FTIR) and Raman spectroscopy, are potent non-destructive chemical characterization techniques that allow for reliable polymer typing and, in some cases, semi-quantitative evaluation. Newer advances in micro-FTIR, confocal Raman, and improved spectroscopic methods are also reviewed. These methods are complemented by thermoanalytical and mass spectrometric techniques, including heat extraction desorption GC/MS and pyrolysis-GC/MS, which enable the robust detection of polymers even in highly heterogeneous or digested samples and facilitate mass quantification. A comparative analysis highlights the advantages, disadvantages, and complementary nature of these methods. In the case of wastewater microplastic studies, thermal analysis, spectroscopy, and microscopy provide a flexible toolkit that facilitates an accurate assessment, methodological consistency, and understanding of sources, routes, and treatment performance.