<p>The term “forensics” refers to the use of scientific knowledge to solve legal problems, especially the scientific analysis of physical evidence that serves as testimony in a court of law. For this purpose, the collected information and evidence are studied and analyzed by various methods, and the results obtained are interpreted in an interdisciplinary way by well-trained specialists in chemistry, biology, psychology, mathematics, or other fields, as appropriate, so that the final conclusions are strongly supported by science. This review presents the fundamental role of thin-layer chromatography (TLC) in the forensic investigation of the following compounds: (1) drugs of abuse with action on the central nervous system in case of long-term use or overdose (depressants, stimulants, synthetic/semisynthetic/natural drugs in various dangerous combinations, and performance-enhancing drugs); (2) plant alkaloids used for recreational/toxic purposes; (3) pesticides with possible forensic action caused by side effects or poisoning; (4) inks from forensic documents; (5) warfare agents; and (6) powerful explosives. By coupling offline/online high-performance TLC (HPTLC) with techniques such as ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, as well as mass spectrometry for visualization/identification/quantification of compounds, followed by chemometric interpretation of the results, HPTLC becomes a powerful and successful tool in forensic science. The results obtained can be considered an essential and powerful starting point in the analysis of forensic evidence, providing basic/solid/useful information, if other instrumental analytical techniques (spectroscopy, mass spectrometry, and chromatography) are necessary owing to the complexity and nature of the evidence and/or if this information needs to be presented in court.</p>