The pharmacokinetic parameters of tylvalosin were studied following intravenous and oral (single & repeated) administrations in normal and experimentally Mycoplasma gallisepticum infected broiler chicken . Following a single intravenous injection of 25 mg tylvalosin /kg b.wt. in normal chicken, tylvalosin could be detected therapeutically for 24 hours post intravenous injection. The serum concentration – time curve of tylvalosin following intravenous injection showed that the drug obeyed a two compartments open model with elimination half- life (t0.5(β) = 7.01 ± 0.251h hours), volume of distribution (Vdss = 5.36 ± 0.115 L/kg ) and total body clearance of the drug (CLtot = 0.71±0.005 L/hr/kg ). Following a single oral administration of 5 mg/kg body weight tylvalosin in normal chickens, the peak plasma concentration ( Cmax) was 1.36 ± 0.009 µg/ml was achieved at a maximum time ( Tmax) of 2.37± 0.023 hour . The oral bioavailability of tylvalosin in normal chicken was 44.28 ± 0.78%. Oral administration of 25 mg tylvalosin per kilogram body weight once daily for five consecutive days in normal and Mycoplasma gallisepticum infected chicken revealed a lower significant serum tylvalosin in Mycoplasma gallisepticum infected chickens compared with normal chickens.