Introduction: Postcardiac surgery complications prolong length of stay (LOS). However, each complication's individual impact on LOS as a continuous variable has not been studied. The purpose of this study was to determine the risk-adjusted increase in LOS associated with individual postoperative complications following cardiac surgery. Methods: All coronary artery bypass and grafting (CABG)-only, CABG + valve, and valve-only patients in the American College of Surgeons National Surgical Quality Improvement Program participant use file, 2005-2018 were evaluated. A negative-binomial model adjusting for the effect of preoperative characteristics and 18 postoperative complications was used to generate incidence rate ratios. This model was used to estimate risk-adjusted increases in LOS for each complication. Results: Of 29,544 patients, 18,184 (61.6%) were CABG only, 8304 (28.1%) were valve only, and 3056 (10.3%) were CABG + valve, with a median LOS of 6.9 d. The most frequent complications were bleeding requiring transfusion (49.2%), prolonged ventilation (6.0%), and pneumonia (4.1%). Infectious complications, including deep surgical site infection (+18.9 d), postoperative septic shock (+17.2 d), organ space infection (+16.7), and wound dehiscence (+15.9), were associated with the largest increases in LOS, followed by respiratory complications, including unplanned reintubation (+12.5) and prolonged ventilation (+10.9). Bleeding or postoperative transfusion (+0.6) had the least effect on extending LOS. Conclusions: After risk adjustment for preoperative patient characteristics and other postoperative complications, all postcardiac surgery complications except myocardial infarction were associated with prolonged LOS, ranging from +0.6 d with bleeding requiring transfusion to +18.9 d with deep surgical site infection. The results of this study provide useful evidence for quality improvement initiatives and informing patients and providers on the expected duration of hospital stay following cardiac surgery with and without complications. <feminine ordinal indicator> 2025 Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.