Phenolic acids (PAs) are one of the utmost prevalent classes of plant-derived bioactive chemicals. They have a specific taste and odor, and are found in numerous medicinal and food plants, such as Cynomorium coccineum L., Prunus domestica (L.), and Vitis vinifera L. Their biosynthesis, physical and chemical characteristics and structure–activity relationship are well understood. These phytochemicals and their derivatives exert several bioactivities including but not limited to anticancer, cardioprotective, anti-inflammatory, immune-regulatory and anti-obesity properties. They are strong antioxidants because of hydroxyl groups which play pivotal role in their anticancer, anti-inflammatory and cardioprotective potential. They may play significant role in improving human health owing to anticarcinogenic, anti-arthritis, antihypertensive, anti-stroke, and anti-atherosclerosis activities, as several PAs have demonstrated biological activities against these disease during in vitro and in vivo studies. These PAs exhibited anticancer action by promoting apoptosis, targeting angiogenesis, and reducing abnormal cell growth, while anti-inflammatory activity was attributed to reducing proinflammatory cytokines. Pas exhibited anti-atherosclerotic activity via inhibition of platelets. Moreover, they also reduced cardiovascular complications such as myocardial infarction and stroke by activating Paraoxonase 1. The present review focuses on the plant sources, structure activity relationship, anticancer, anti-inflammatory and cardioprotective actions of PAs that is attributed to modulation of oxidative stress and signal transduction pathways, along with highlighting their mechanism of actions in disease conditions. Further, preclinical and clinical studies must be carried out to evaluate the mechanism of action and drug targets of PAs to understand their therapeutic actions and disease therapy in humans, respectively.