Carnosic acid (CA), a polyphenolic diterpene naturally found in Rosmarinus officinalis, has demonstrated a wide range of pharmacological activities according to scientific research, making it a key candidate for new therapeutic product development. The aim of this manuscript is to present an updated review of the literature on the latest research findings about carnosic acid, emphasizing its most relevant biological functions. Accordingly, this work highlights the main reported pharmacological activities, such as antioxidant, antidiabetic, anti-inflammatory, antimicrobial, antiobesity, anticancer, and neuroprotective properties. We conducted a systematic search of bibliographic databases for peer-reviewed literature based on a specific review question, utilizing scientific databases including PubMed, Scopus, Science Direct, and Google Scholar published since 1990. Numerous studies have highlighted the extensive therapeutic applications of carnosic acid. Among others, carnosic acid was found to have antioxidant, antidiabetic, anti-inflammatory, antimicrobial, antiobesity, anticancer, and neuroprotective activities. Further, carnosic acid displayed low toxicity levels and few side effects. CA shows great promise as a therapeutic agent in the prevention and treatment of many diseases, such as numerous cancers, infectious diseases, and newly emerging illnesses like Alzheimer’s and Parkinson’s diseases. In recent times, there has been a significant push to improve PBMs, proposing their application as natural drugs for several pathological conditions, with a focus on their anti-inflammatory and antioxidant capabilities. Carnosic acid exhibits antidiabetic, antimicrobial, antiobesity, and neuroprotective effects, as well as antitumor, anti-infectious, CNS, and endocrine system activities. However, further research on its precise pharmacological mechanisms is required before it can be reliably used to treat human diseases.