Psidium involutisepalum, a new species of Myrtaceae, is described and illustrated. The species is easily recognized by the combination of floral buds with calyx minute, truncate or rounded, 0.2–0.5 × 0.5–1 mm, involute in fruit, facing the receptacle. The fruits are rounded to pyriform, 20–30 × 13–20 mm, yellow when mature, glabrous, striate, sepals involute, facing the receptacle, seeds 1–6, 7–9 × 6–7 mm, rounded to angular. Based on the types and specimens examined, literature survey and the rules of international code of nomenclature, Psidium turbinatum is recognized here as a legitimate name. The relationship of Psidium involutisepalum, P. myrtoides, and P. turbinatum is discussed and comments concerning their taxonomy and ecology are also provided.