Pseudostem subcylindrical, 2.5 m or taller, tufted. Inflorescence slightly curved and pendulous; bractsovate-lanceolate, 7-8 cm wide, strongly concave, dark purplish red; flowers 8 per bract, arranged in 2 series, sessile; Male flowers: periath cylindrical, 3-3.3 cm long, 5-lobed (3 lobes in outer row, 2 lobes in inner row); lobes of outer row: lateral ones oblong-triangular, 5-5.5 mm long, ca. 4 mm wide, obtuse, entire; central one ovate, 3.5 mm long and wide, obtuse; lobes of inner row obliquely ovate, ca. 4-4.5 mm long, 3 mm wide, obtuse, base cordate or auricule; posterior lobe of inner row always free, elliptic-obovate, 1.5-2 cm long, ca 1 cm wide, truncate or emerginate, and shortly cuspidate at apex; stamens 5, equalling perianth or shorter; filaments green, filiform, ca 1 cm long; anthers linear, connective slightly elongate, style column filiform, equalling stamens apex, clavate. Female flowers unknown. Rachis terete, 3 cm in diam., densely pubescent. Immature fruits obliquely tetragonal, stipitate; fruiting stalk densely pubescent.
Musa insularimontana is reduced to only 6 sites within 50m. Endemic to primary forest on the southern part of Lanyu Island, Taiwan at 290m elevation.