Adiantum species, commonly known as maidenhair ferns, belong to the Pteridaceae family and have been utilized in traditional medicine across various cultures for treating respiratory ailments, skin disorders, inflammation, and other conditions. This chapter reviews the biomedical sciences of key Adiantum species, focusing on their phytochemistry and validated pharmacological activities, including antimicrobial, antioxidant, anti-inflammatory, anticancer, and antidiabetic effects, as reported in recent studies up to 2025. Over 130 bioactive compounds, including flavonoids (rutin, quercetin, luteolin), phenolic acids (chlorogenic acid, and caffeic acid), and terpenoids, underpin these properties, with promising in vitro, in vivo, and in silico evidence. Despite low toxicity profiles, clinical trials remain scarce, highlighting the need for standardized extracts, mechanistic studies, and therapeutic formulations. Recent advancements in extraction techniques, like supercritical fluid extraction, enhance compound isolation for biomedical applications.