Within species of birds, variation in plumage may allow potential mates or competitive rivals to quickly assess the quality of an individual. Little is known about the role of white tail feather patches (“tail white”) in male Cerulean Warblers (Setophaga cerulea) and whether variation in patch size could serve as a signal. We hypothesized that the size of tail white patches in males acts as an honest signal of quality, with larger white patches indicating high quality males. We measured and compared the area of tail white to four estimates of quality (age, structural size, body mass, and blood parasite load) in 71 male Cerulean Warblers at the Queen’s University Biological Station in eastern Ontario. We found that males 2 years old or older had significantly larger tail white patches than 1 year old males, and that structurally larger males (estimated by wing length) had significantly larger tail white patches than smaller males. Our best-performing statistical model suggested that heavier individuals had larger areas of tail white, but this relationship depended on wing length: white positively covaried with body mass in smaller individuals (shorter wings), but not in larger individuals. Our findings suggest that size of tail white patches may provide information on some, but not all, aspects of quality of male Cerulean Warblers; however, we do not know if this information is perceived and used by other Cerulean Warblers in nature.