The grapsoid and gall crab fauna of Easter Island is reviewed, based on historical records and material collected by the Science Museum of Long Island Easter Island Expedition of 1998–1999. Previously, nine grapsoids identified to the species level, but no gall crabs, were recorded from the island. The present work reports on eight species of grapsoids: Pachygrapsus laevimanus Stimpson, 1858 (previously recorded from the island as Pachygrapsus transversus [Gibbes, 1850]); Pachygrapsus plicatus (H. Milne Edwards, 1837) (new record); Leptograpsus variegatus (Fabricius, 1793); Cyclograpsus longipes Stimpson, 1858; Ptychognathus easteranus Rathbun, 1907; Percnon pascuensis Retamal, 2002 (redescribed and figured); Guinusia dentipes (De Haan, 1835); and Guinusia integripes (Garth, 1973) (new combination). Geograpsus crinipes (Dana, 1851) and Guinusia chabrus (Linnaeus, 1758) have been previously recorded from the island; no material of the former was collected and the latter is considered an erroneous identification of Guinusia dentipes. Dacryomaia japonica (Takeda & Tamura, 1981) is the first identified gall crab from the island. Color notes for six species and illustrations for several important morphological characters of Percnon pascuensis are provided.