The chemical diversity of plants underpins their extensive use in medicine, cosmetics, and industry. This study utilizes Fourier Transform Infrared (FTIR) spectroscopy to identify and characterize the functional groups present in five medicinal plants: Curcuma longa (turmeric), Mentha piperita (peppermint), Aegiceras corniculatum (mangrove), Zingiber officinale (ginger), and Piper nigrum (black pepper). FTIR spectroscopy is a non-destructive, rapid technique that identifies molecular vibrations associated with functional groups such as O-H, C-H, C=O, and N-H, facilitating the characterization of both organic and inorganic compounds. The plants analyzed are known for their therapeutic properties, including antioxidant, antimicrobial, anti-inflammatory, and anticancer effects. The FTIR spectra revealed the presence of various functional groups, including hydroxyl, carbonyl, aliphatic C-H, and aromatic groups. The fingerprint region (600–1500 cm⁻¹) exhibited complex absorption bands specific to each plant, reflecting the molecular structure and chemical composition of their bioactive compounds. Unique spectral features such as metal-ligand vibrations in Aegiceras corniculatum highlight the diverse phytochemical profile of this plants. This study underscores the potential of FTIR spectroscopy in identifying bioactive compounds, facilitating their applications in pharmaceutical and nutraceutical development, and contributing to the growing database of FTIR spectral signatures for medicinal plants.