This case series describes polycystic kidney disease in 3 (2 male, 1 female) 2-month-old, juvenile rainbow lorikeets (Trichoglossus moluccanus). The lorikeets diagnosed with polycystic kidney disease were the progeny of full sibling parents that were being intentionally line bred for the purpose of establishing a rainbow lorikeet with the blue color mutation. Clinically the juvenile lorikeets were presented with clinical signs of lethargy, dehydration, regurgitation, anorexia, polyuria, and pelvic limb paresis. Multiple abnormalities were identified on the complete blood count and plasma biochemistry panel, including a normocytic normochromic nonregenerative anemia, hyperuricemia, hyperphosphatemia, hypercalcemia, and azotemia. Severe renal dysfunction was diagnosed in all birds on the basis of clinical presentation, physical examination, and complete blood count and plasma biochemistry results. Radiographically marked renomegaly was noted in one of the cases. Although intensive critical care and supportive therapy was provided, 1 lorikeet died, and the remaining 2 were euthanatized because of client financial constraints and a rapid deterioration of their clinical condition associated with severe renal dysfunction. Postmortem pathology results found that all birds had marked renomegaly, visceral gout, and polycystic kidney disease. Because of the age of the birds and the line breeding within this group of lorikeets, the disease was believed to be inherited. Polycystic kidney disease should be considered as a possible differential diagnosis in juvenile psittacine birds with a history of line breeding when presented with severe renal dysfunction. From the current case series, polycystic kidney disease appears to carry a grave prognosis in juvenile rainbow lorikeets.