The association of AKI after pediatric cardiac surgery with long-term CKD and hypertension development is unclear. The study objectives were to determine whether AKI after pediatric cardiac surgery is associated with incident CKD and hypertension. This was a prospective cohort study of children of 1 month to 18 years old who were undergoing cardiac surgery at two tertiary care centers (Canada, United States). Participants were recruited before cardiac surgery and were followed during hospitalization and at 3, 12, 24, 36, and 48 months after discharge. Exposures were postoperative AKI, based on the Kidney Disease Improving Global Outcomes (KDIGO) definition, and age <2 years old at surgery. Outcomes and measures were CKD (low eGFR or albuminuria for age) and hypertension (per the 2017 American Academy of Pediatrics guidelines) at follow-up, with the composite outcome of CKD or hypertension. Among 124 participants, 57 (46%) developed AKI. AKI versus non-AKI participants had a median (interquartile range) age of 8 (4.8-40.8) versus 46 (6.0-158.4) months, respectively, and higher preoperative eGFR. From the 3- to 48-month follow-up, the cohort prevalence of CKD was high (17%-20%); hypertension prevalence was also high (22%-30%). AKI was not significantly associated with the development of CKD throughout follow-up. AKI was associated with hypertension development at 12 months after discharge (adjusted relative risk, 2.16; 95% confidence interval, 1.18 to 3.95), but not at subsequent visits. Children aged <2 years old at surgery had a significantly higher prevalence of hypertension during follow-up than older children (40% versus 21% at 3-month follow-up; 32% versus 13% at 48-month follow-up). CKD and hypertension burden in the 4 years after pediatric cardiac surgery is high. Young age at surgery, but not AKI, is associated with their development.