Tacrolimus granules were developed for patients who are unable to swallow capsules. Therapeutic drug monitoring (TDM) is required to optimize efficacy and safety, which is based on C for tacrolimus capsules. Pharmacokinetic (PK) data for tacrolimus granules are required to establish the basis for TDM in those who are unable to swallow capsules. In this phase IV study (NCT01371331) of children undergoing liver, kidney, or heart transplantation, patients received tacrolimus granules 0.15 mg/kg twice daily; first dose was administered within 24 hours of reperfusion. PK analysis samples were collected after reperfusion, after first dose of tacrolimus (Day 1), and at steady state (Day 7; >4 days stable dose). Of the 52 transplant recipients enrolled, 38 had two evaluable PK profiles. Mean AUC after first dose of tacrolimus was 211, 97, and 224 hour*ng/mL in liver, kidney, and heart transplant recipients, respectively; corresponding mean AUC at steady state was 195, 208, and 165 hour*ng/mL. C and AUC were positively correlated after first dose of tacrolimus and at steady state (Pearson's coefficients: r = 0.81 and r = 0.87, respectively). This study demonstrated that C is a reliable marker for TDM in pediatric transplant recipients treated with tacrolimus granules, consistent with TDM for other tacrolimus formulations.