Abstract: Parental care in birds may be provided by one sex or both depending on the maturity of the chicks at hatching and is provided especially to altricial nestlings. These often need both mother and father to provide food for them during their stay in nest. The amount of care the parents provide to the young affects their growth and development between hatching and fledgling and increases the chances of the nestlings surviving. Growth and development of the Asian Paradise Flycatcher were studied during the breeding season from 2005-2009 at Chiang Dao Wildlife Research Station, Chiang Mai Province and Khao Pra-Bang Khram Wildlife Sanctuary, Krabi and Trang Province. About 29 nestlings were measured (length of bill, unflattened wing and tarsus and body-weight) and their plumage development scored. All the measurements were highly correlated with the age of nestlings during their period in the nest except that body weight in the day before fledgling fell slightly. The body sizes of nestlings of Rufous-plumaged males with long central tail feathers (RL) and Rufous-plumaged males with short tails (RS) were also compared. The growth curves of nestlings of RL and RS males were nearly identical and there were no significant differences between them. The plumage developed gradually and was divided into 4 stages. The nestlings opened their eyes fully on day 7-8 and left the nest on day 10-11 before they were able fly properly. The nestlings made a begging call with their neck stretched out to try to reach the parent’s bill and their gape opened so that their yellow palate was visible. A successful breeding cycle lasted 24-30 days including 2-4 days of egg-laying, 12-15 days of incubation and 10-11 days of parental care of nestlings in the nest. Fledgling success was 44.4%.