The object of this study was to establish a minimum dose of ultraviolet B (UVB) radiation capable of producing an erythemal reaction in budgerigars (Melopsittacus undulatus), to determine a threshold dose of UVB for vitamin D photoconversion, and to investigate the use of safer UVB wavelengths. In each of 5 experiments of this study, 20 birds were divided into a control group (n = 10) and a UVB irradiated group (n = 10). Light sources that provide broadband UVB wavelengths (280–315 nm) and narrowband UVB (310–320 nm) were used. Varied doses of UVB radiation were administered to budgerigars by altering exposure time and irradiance. Safety was determined by observing body weight and incidence of photokeratitis and photodermatitis. Efficacy was evaluated by measuring changes in serum 25-hydroxycholecalciferol levels. Serum corticosterone was measured in 1 experiment to monitor stress levels. The results demonstrated that exposure to 180 mJ/cm² broadband UVB induced vitamin D photoconversion, decreased body weights, and increased serum corticosterone levels. At these wavelengths, UVB-induced lesions were observed. A broadband UVB of 150 to 300 mJ/cm² was determined as the minimum erythema dose, and the threshold dose for vitamin D photoconversion was calculated to be in the range of 113–225 mJ/cm². No erythemal lesions or vitamin D photoconversion took place after exposure to up to 1730 mJ/cm² narrowband UVB radiation. A minimum erythema dose and a threshold dose for vitamin D conversion need to be determined for each species if phototherapy is to be considered as a safe and effective therapeutic or husbandry tool.