This systematic review and meta-analysis evaluated whether hyperoncotic 20%–25% human albumin affects acute kidney injury after adult on-pump cardiac surgery. Across four studies including 6,651 patients, albumin was associated with a modest but consistent increase in postoperative AKI risk compared with crystalloids or 4%–5% albumin. Risk appeared similar whether albumin was given during surgery or within 24 hours afterward, supporting cautious, selective use.