Aim: To evaluate drug–drug interaction (DDI) between tacrolimus (TAC) and different formulations of voriconazole (VRCZ) in adults and pediatrics with different ages. Method: Physiologically based pharmacokinetics (PBPK) models were used to evaluate DDI between oral TAC and different formulations of VRCZ (oral and intravenous (IV) formulations) in adults and pediatrics with different age groups. Both single dose and multiple dose administration were assessed. Multiple dosage regimens were maintained for 7 days. Result: A higher IV dose might lead to a great increase in area under the plasma concentration-time curve (AUC) and maximum concentrations (Cmax) of TAC in both adults and pediatrics. Besides, compared with IV administration, these two PK values of TAC increased more when combined with VRCZ orally. The ratio of two PK values increased with the age growth in pediatrics. And it increased progressively to adult values at the age of 3-8 years. Tacrolimus liposolubility was the most significant parameter on the DDI between TAC and VRCZ. Conclusion: In pediatric population, VRCZ had a less impact on PK of TAC than that in adults. The DDI progressed gradually as the age advances in pediatrics and finally equal to adults. Oral VRCZ increased PK parameters of tacrolimus even more than IV administration. Personalized dosage adjustment should be considered in clinical practice when co-administrated with VRCZ, especially in adults or in oral formulation.