Background: For colorectal liver metastases, surgery is a high-risk procedure due to perioperative morbidity. The objective was to assess severity of complications after fast-track liver surgery for colorectal liver metastases and their impact on morbidity and mortality. Methods: All patients were treated according to the same fast-track programme. Complications were graded according to the Clavien–Dindo classification for patients undergoing surgery from 2013 to 2015. Correlation between complications and length of stay was analysed by multivariate linear regression. Results: 564 patient cases were included of which three patients died within 3 months (0.53%, 95% CI: 0.17–1.64%). Complications were common with Grade ≤ 2 in 167 patients (30%) and ≥ Grade 3a in 93 (16%). Patients without complications had a mean length of stay of 4.1 days, which increased with complications: 1.4 days (95% CI: 1.3–1.5) for Grade 2, 1.7 days (1.5–2.0) for Grade 3a, 2.3 days (1.7–3.0) for Grade 3b, 2.6 days (1.6–4.2) for Grade 4a, and 2.9 days (2.8–3.1) for Grade 4b. Following were associated with increased length of stay: complication severity grade, liver insufficiency, ascites, biliary, cardiopulmonary, and infectious complications. Conclusions: Complications after liver surgery for colorectal liver metastases, in a fast track setting, were associated with low mortality, and even severe complications only prolonged length of stay to a minor degree.