Tirzepatide is a first-in-class glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist approved as for the treatment of type 2 diabetes mellitus. A population-based pharmacokinetic (PK) model was developed from 19 pooled studies. Tirzepatide pharmacokinetics were well-described by a two-compartment model with first order absorption and elimination. The tirzepatide population PK model utilized a semimechanistic allometry model to describe the relationship between body size and tirzepatide PK. The half-life of tirzepatide was ~5 days and enabled sustained exposure with once-weekly subcutaneous dosing. The covariate analysis suggested that adjustment of the dose regimen based on demographics or subpopulations was unnecessary. The tirzepatide PK model can be used to predict tirzepatide exposure for various scenarios or populations.