ABSTRACT Aims: This study aimed to develop a PBPK model for tacrolimus incorporating CYP3A5 and CYP2C19 polymorphisms to predict the DDIs between tacrolimus and voriconazole. Methods: Pharmacokinetic (PK) data in rats and healthy subjects receiving tacrolimus with and without voriconazole were used for model development and evaluation. Then, we used the final model to simultaneously investigate the effect of CYP3A5 and CYP2C19 polymorphisms on the PK data of tacrolimus when combined with voriconazole. Results: The final results showed that the predicted Cmax in CYP3A5 nonexpressers was 1.5-fold higher than expressers, and the predicted AUC0-∞ was 1.92 to 1.96-fold higher in nonexpressers. However, the Cmax and AUC0-∞ of tacrolimus both have no significant difference between different CYP2C19 metabolizers. Conclusions: A physiologically-based pharmacokinetic (PBPK) model for tacrolimus integrated with CYP3A5 and CYP2C19 polymorphisms was successfully established, providing more insights regarding the DDIs between tacrolimus and voriconazole in patients with different CYP3A5 and CYP2C19 genotypes. Furthermore, this study highlights the feasibility of PBPK modeling to predict DDIs between these two drugs and the need to include CYP3A5 polymorphisms but not CYP2C19 polymorphisms.