Petroselinum crispum (parsley), a widely cultivated herb, is recognized worldwide for both its culinary value and medicinal potential. Traditionally, parsley has been used in many cultures as a spice and as a herbal remedy for conditions such as hypertension, diabetes, inflammatory disorders, digestive problems, and urinary tract diseases. The plant contains a wide range of bioactive constituents, particularly flavonoids, phenolic acids, coumarins, terpenoids, and fatty acids, which contribute to its diverse biological activities. Experimental studies have demonstrated that parsley exhibits multiple pharmacological properties, including antioxidant, antimicrobial, anti-inflammatory, diuretic, antidiabetic, hepatoprotective, cardioprotective, and neuroprotective effects. Additional activities such as anti-fatigue, estrogenic, immunomodulatory, and anticancer effects have also been reported. These biological activities are largely attributed to its rich phytochemical composition, especially flavonoids and phenolic compounds. However, despite its promising therapeutic potential, most available evidence is derived from preclinical studies, and clinical data in humans remain limited. Furthermore, certain compounds such as apiole and myristicin may pose safety concerns when parsley is consumed in excessive amounts or as concentrated extracts. This review provides a comprehensive overview of the ethnobotanical uses, phytochemical constituents, pharmacological activities, and safety considerations of P. crispum, highlighting its potential as a functional food and medicinal plant. The findings suggest that parsley represents a promising natural source of bioactive compounds for the management of various health conditions, although further well-designed clinical studies are required to confirm its efficacy, clarify mechanisms of action, and ensure its safe therapeutic application.