Justicia adhatoda L. (J. adhatoda L.) belongs to the family of Acanthaceae and is a well-known medicinal plant in the South and Southeast Asia. The phytochemicals isolated from the plant include alkaloids, flavonoids, phenolic acids, triterpenoids, steroids and glycoside derivatives that are responsible for its diverse medicinal properties. The information was obtained from literature, sources including books, research papers, review papers and reports available online in accepted scientific databases such as Science Direct, Taylor and Francis, Frontiers, Scopus, Springer, MDPI, MEDLINE, Pubmed, Wiley. This review presents the up-to-date data information available on J. adhatoda L. After careful consideration, a total of 98 articles were used for this review. Herbal medicine is a form of healthcare that has been used for years in many countries. Justicia adhatoda L. is one such multipurpose plant with many uses, health benefits, and bioactivities. Several studies revealed the presence of approximately 233 phytochemical constituents. Abundance of these bioactive phytochemicals confer various pharmacological activities such as anti-microbial activity, antioxidant activity, anti-inflammatory activity, antipyretic activity, insecticidal properties, hepatoprotective activity, anti-diabetic activity, anti-tubercular activity, anti-cancer and radioprotective activity, anti-ulcer activity and activity against respiratory ailments. The review provides an overview of the traditional uses, phytochemistry, pharmacological activity and toxicology of J. adhatoda L. For future drug design and discovery from J. adhatoda L. more activity screening and structure–activity relationship studies are required to explore further. This present review brings forth the current findings on the pharmacological activities of J. adhatoda L. but there are still certain aspects of the plant that are limited, not reliable, or lacking in data. Also there need to be development of methods to isolate active compounds from other parts of the plant other than the leaves and to study their phytochemical potential.