The common kestrel (Falco tinnunculus) is a common raptor found worldwide. To establish reference intervals for cardiac size by radiography, 14 adult common kestrels were evaluated clinically and with radiographs (lateral and ventrodorsal views). The cardiac width, thoracic width, distance between third and fourth ribs, synsacrum width, coracoid width, and distance between clavicle bones were measured on ventrodorsal radiographs. The ratio between cardiac width and the other 5 indices was calculated. Results showed a significant, positive correlation between the cardiac width and thoracic width and between cardiac width and coracoid width. The values and ratios of this study can be used as reference intervals for cardiac size evaluated radiographically in the common kestrel for diagnosis of the cardiomegaly in this bird.