Chlamydiosis is an important cause of morbidity and mortality in cockatiels (Nymphicus hollandicus); however, little published information is available regarding effective treatment options for this species. This preliminary study was conducted to determine if adequate plasma concentrations of doxycycline, the antibiotic of choice for treating chlamydiosis in pet birds, could be achieved in cockatiels by using different methods of administration. Doxycycline hyclate was administered to 5 groups comprising 3 to 6 birds each by intramuscular injection (100 mg/kg IM every 10 days for 5 injections) or by mixing with drinking water (0.28 or 0.83 mg/ml), seeds (500 mg/kg wet weight), or mash (1000 mg/kg). Three additional groups of birds received unmedicated food and water and served as controls. Plasma doxycycline concentrations were measured periodically during the 45-day trial. Birds given doxycycline by intramuscular injection had variable, localized tissue reactions and a mean trial plasma concentration <1 μg/ml, the value considered therapeutic for treating chlamydiosis. Birds that received doxycycline in drinking water and in seeds maintained group mean doxycycline concentrations >1 μg/ml. Birds that received doxycycline in mash had high plasma doxycycline concentrations and showed severe clinical illness, suggesting doxycycline toxicosis; drug administration was discontinued on day 3. Therefore, in this study, drinking water and seeds were effective vehicles for doxycycline administration to clinically healthy cockatiels under controlled conditions. However, mash combined with doxycycline resulted in severe toxicosis, whereas doxycycline hyclate by intramuscular injection did not achieve desired therapeutic plasma concentrations. Further studies are needed to examine efficacy and safety of food- and water-based doxycycline regimens in clinically ill birds and those housed under different environmental conditions.