Population pharmacokinetics of vancomycin in Thai adult patients was determined by non-linear mixed-effects approach using 319 vancomycin serum concentrations from 212 patients. The data were best fitted by a two-compartment model and it was used to examine the effect of patient characteristics on the vancomycin pharmacokinetics. In the final model, there was a linear relationship between vancomycin clearance, CL (L/h), and creatinine clearance calculated by Cockcroft-Gault equation, CL(Cr) (mL/min): CL = 0.044 × L(Cr). Meanwhile, volume of central compartment, V(1) (L), was linearly related with the age (years old): V(1) = 0.542 × Age. Intercompartment clearance (Q) and volume of peripheral compartment (V(2)) was 6.95 L/h and 44.2 L, respectively. The interindividual variability for CL, V(1), Q, and V(2) was 35.78, 20.93, 39.50, and 57.27%, respectively. Whereas, the intraindividual variability was 4.51 mg/L. Final model then was applied to predict serum vancomycin concentrations on validation group. Predictive performance revealed a bias of -1.43 mg/L (95% CI: -5.82-2.99) and a precision of 12.2 mg/L (95% CI: -1.60-26.16). In conclusion, population pharmacokinetic of vancomycin in Thai adult patients was developed. The model could be used to create vancomycin dosage regimen in the type of patient similar with the present study.