North American wood-warbler species (Parulidae) studied to date have song systems of one or two categories. Those with two categories use them in different temporal and behavioral contexts, which suggests similar functions across species. We conducted the first detailed analysis of the vocal behavior of a species in the genus Cardellina, the Canada Warbler (C. canadensis). We found that males had two performance-encoded song categories, Mode I and Mode II, and used them in contexts similar to those in which parulids of the genera Vermivora, Mniotilta, and Setophaga use their song categories. Males sang Mode I more often during the day, when unpaired, during early nesting, and when alone or near a female. Males sang Mode II at dawn, after pairing, during the postfledging period, and when near another male. In Mode I, males sang more stereotyped songs more slowly and regularly. In Mode II, males sang more variable songs rapidly, with a more variable rhythm, and chipped frequently between songs. Although each male included phrases in Mode II songs that he did not use in Mode I, the same phrases were used by other males in Mode I, which indicates that song categories were not form-encoded. Unlike Setophaga species with performance-encoded categories, individual males used most (80%) of their phrases in both categories. The song system of the Canada Warbler, two performance-encoded categories without separation of individuals' repertoires into two distinct parts, is unique among parulids studied thus far, and may provide insight into the evolution of parulid repertoire specialization.