Cajanus cajan (pigeon pea) is a nutritionally and medicinally important legume that has emerged as a rich source of bioactive stilbenoids, flavonoids, and phenolic compounds with diverse pharmacological properties. Phytochemical investigations have identified several biologically active constituents, including cajaninstilbene acid, cajanol, pinostrobin, orientin, vitexin, quercetin derivatives, and numerous novel stilbenoids exhibiting antioxidant, anti-inflammatory, antimicrobial, antidiabetic, anticancer, neuroprotective, and hepatoprotective activities. Early ecological studies demonstrated that phenolic compounds present on pigeon pea pod surfaces influence insect feeding behavior, suggesting an intrinsic defense role of these metabolites. Subsequent pharmacological studies revealed modulation of oxidative stress, inflammatory signaling, glucose metabolism, apoptosis, and cellular survival pathways.