The traditional system of medicine consists of a large number of plants with various medicinal and pharmacological importance. Bengal has a rich reserve of medicinally important plants in the Sundarbans deltaic region with a diverse population of mangrove plants scientifically proven to be of immense pharmacological importance. Excoecaria agallocha L. is a milky mangrove widely distributed in Indian coastal areas. This chapter provides a comprehensive review of the complete profile of the important mangrove plant Excoecaria agallocha (Euphorbiaceae) and elaborately describes the ethnobotany, phytochemistry, and pharmacological properties. There are almost 20 different polyphenols, 15 terpenoids, and more than 50 volatile derivatives that have been identified from leaves, stems, latex, and root extract. An enormous number of compounds and phytoconstituents have been isolated from the plant, which are mainly diterpenoids, triterpenoids, flavonoids, sterols, and a few other compounds. E. agallocha has huge amounts of polyphenols and terpenoids, reported to have endocrine, epidemic, and endemic disease control as anti-microbial, anti-cancer, and anti-diabetic agents. It is used traditionally in the treatment of various diseases, such as epilepsy, ulcers, leprosy, rheumatism, and paralysis. The plant also has many pharmacological activities, such as antioxidant, antimicrobial, anti-inflammatory, analgesic, antiulcer, anticancer, antidiabetic, and antitumor-protecting activities. Hence, this chapter could help guide researchers anticipating further investigations in these directions.