The Coiba Spinetail (Cranioleuca dissita), endemic to Islas Coiba and Ranchería on the Pacific coast of Panama, was originally classified as a subspecies (C. d. dissita) of the geographically distant Rusty-backed Spinetail (C. vulpina) of South America, but its status has long been an enigma. The present study was conducted to obtain basic information on the ecology, behavior, and vocalizations of this species, which has previously been lacking. On both islands, Coiba Spinetail was found almost exclusively in forest and forest edge. Their most common foraging substrate was small-diameter (∼1 cm) branches or vines, although they also foraged on tree trunks. The foraging type most often observed was pecking, but probing and gleaning were also observed regularly. The most common foraging height was 7–10 m above the ground, although they foraged as low as 2 m and as high as 25 m. The nest of Coiba Spinetail, which has not been previously described, is a globe-shaped structure made mostly of plant fibers and built around a vertical support such as an upright branch or trunk or around several lianas or vines. The nest of Rusty-backed Spinetail instead is a globular mass of grass, roots, and sticks, wedged in the fork of a partly submerged sapling or bush. The song of Coiba Spinetail resembles typical Cranioleuca spp. in having several short introductory notes followed by a series of notes on one pitch. It differs from most species in the genus, however, in that the notes gradually become longer and slow down, rather than accelerating or being evenly spaced. The song differs markedly from that of Rusty-backed Spinetail in note structure and quality. These results coupled with previous findings that Coiba Spinetail is genetically distinct from Rusty-backed Spinetail indicate that it merits full species status. Considering its extremely small range, Coiba Spinetail qualifies for Near Threatened status under IUCN Red List criteria.