Concurrent resection of the primary cancer and synchronous colorectal cancer liver metastases (CRCLM) was evaluated for differences in outcomes following stratification of both the liver and colorectal resection. Consecutive cases of synchronous resection of both the CRC primary and CRCLM were reviewed retrospectively at a single, high-volume institution over a 17-year period (2000–2017). 273 patients underwent simultaneous resection of CRCLM. The distribution of the primary lesion was similar between the colon (52.4%) and rectum (47.6%), while 46.9% of patients had bilobar liver disease. Major liver/major colorectal resection (n = 24) were significantly more likely to experience colorectal specific morbidity (OR 3.98, 95% CI 1.56–10.15, p = 0.004), liver specific morbidity (OR 7.4, 95% CI 2.22–24.71, p = 0.001), total morbidity (OR 2.91, 95% CI 1.18–7.18, p = 0.020) and 90-day mortality (OR 5.50, 95% CI 1.27–23.81, p = 0.023). Failure to receive adjuvant chemotherapy secondary to postoperative morbidity was associated with significantly worsened survival (HR for death 5.91, 95% CI 1.59–22.01, p = 0.008). Postoperative morbidity precluding the administration of adjuvant chemotherapy is associated with an increase in mortality. Combining a major liver with major colorectal resection is associated with a significant increase in major morbidity and 90-day mortality, and should be avoided.