Natural products and their derivatives play a crucial role in treating various diseases. Harmine, a tricyclic β-carboline alkaloid isolated from the seeds of Peganum harmala L., has emerged as a promising therapeutic candidate owing to its multifaceted biological activities. Recent studies have further highlighted the enhanced therapeutic potential of harmine derivatives. To assess the current research landscape on harmine and its derivatives, we conducted a comprehensive analysis of studies published between 2019 and 2024 in scientific databases, such as PubMed, Web of Science, and Google Scholar. In this review, the possible applications of harmine and its derivatives were systematically illustrated, including biological activities, structure-activity relationships, and nanotechnology applications. Notably, the biological activities of harmine and its derivatives mainly contained antitumor, neuroprotective, antiparasitic, anti-inflammatory, and antidiabetic properties. In addition, structural modifications and the application of nanocarriers make harmine and its derivatives more druggable. The aim of this review is to summarize the recent advancements in harmine and its derivatives research, analyze emerging trends, and explore their clinical value.