This international study aimed to test the measurement properties of the updated European Organisation for Research and Treatment of Cancer (EORTC) questionnaire module for colorectal cancer, the QLQ-CR29. The QLQ-CR29 was administered with the QLQ-C30, core questionnaire, to 351 patients from seven countries. Questionnaire scaling and reliability were established and clinical and psychometric validity examined. Patient acceptability and understanding were assessed with a debriefing questionnaire. Multi-trait scaling analyses and face validity refined the module to four scales assessing urinary frequency, faecal seepage, stool consistency and body image and single items assessing other common problems following treatment for colorectal cancer. Scales distinguished between clinically distinct groups of patients and did not correlate with QLQ-C30 scales, demonstrating construct validity. The QLQ-CR29 scores were reproducible over time in stable health. The EORTC QLQ-CR29 demonstrates sufficient validity and reliability to support its use to supplement the EORTC QLQ-C30 to assess patient-reported outcomes during treatment for colorectal cancer in clinical trials and other settings.