Abstract Serotonin, also known as 5‐hydroxytryptamine, is an important signaling molecule in the central and peripheral nervous systems of humans. Acting through several receptor types, it helps regulate the normal functioning of the gastrointestinal tract, cardiovascular system and brain. Serotonin signaling has also been implicated in the etiology of several diseases, including depression, anxiety disorders, hypertension and irritable bowel syndrome. The present review focuses on the chemical analysis of serotonin in biological fluids and biomatrices and traces the development and application of early methods based on UV absorbance or fluorescence to more widely used current methods such as high‐performance liquid chromatography coupled to mass spectrometry. A brief summary of the biochemistry, metabolism and physiological roles of serotonin is also presented.