Background Colorectal cancer (CRC) is a common malignancy. There is growing evidence that CRC incidence is increasing in the younger population. There is controversy surrounding the prognosis of young patients with CRC. In this study we reviewed Australian patients with metastatic CRC (mCRC) who were younger than 40 years of age at the time of diagnosis of metastatic disease. To our knowledge this is the first study to focus on this age group with mCRC. Patients and Methods This was a retrospective study using data from the South Australian Metastatic Colorectal Cancer database. We compared patient and disease characteristics, management approaches, and outcomes for age groups < 40 and ≥ 40. A multivariate Cox proportional hazards model was fitted to compare the survival outcomes (death from all causes) between the 2 groups. Results From 3318 patients, 46 (1.4%) were younger than 40 years of age. In a comparison of patients in the younger than 40-year-old group with the older group, a greater proportion had synchronous metastatic disease (80.4% vs. 64.4%, respectively; P =.04) and disease originating from the left colon (71.7% vs. 61.7%, respectively; P =.035); also a larger proportion in the younger than 40-year-old group received chemotherapy compared with the older group (82.6% vs. 58.7%, respectively; P <.01). In the adjusted multivariate model, survival was not significantly different between the 2 groups (hazard ratio, 0.81; 95% confidence interval, 0.56-1.16; log rank P =.25). Conclusion Young-onset mCRC patients, when defined as aged younger than 40 years, have equivalent survival compared with their older counterparts. This is despite differences in disease characteristics and management approach between the 2 groups.