This species can be recognized by its rather robust habit; its distinctive oblanceolate, firm-textured, often rather shiny leaves; its terminal cymose inflorescences; its showy pink corollas with the tube 5-13 mm long and dense yellow bearded pubescence in the throat; and its drupaceous fruits with numerous seeds in each pyrene. Isertia longifolia is apparently frequent in secondary vegetation, and has been collected in both upland (terra firme) and seasonally flooded (várzea) areas.