Evidence is limited regarding the effect of diagnosis-to-treatment interval (DTI) on the survival of colorectal cancer (CRC) patients. In addition, previous studies on treatment delay and CRC survival have largely grouped patients from all stages (I-IV) into one cohort. Our study provides analysis on each stage individually. We conducted a retrospective cohort study with 39,000 newly diagnosed CRC patients obtained from the Taiwan Cancer Registry Database from 2004-2010 to examine the effect of DTIs on overall survival. DTIs were divided into 3 groups: ≤ 30 days (36,115 patients, 90.5% of study patients), 31-150 days (2,533, 6.4%), and ≥ 151 days (1,252, 3.15%). Risk of death was increased for DTI 31-150 days (hazard ratio 1.51; 95% confidence interval 1.43-1.59) and DTI ≥ 151 days (1.64; 1.54-1.76) compared to DTI ≤ 30. This risk was consistent across all cancer stages. Additional factors that increased risk of death include male gender, age >75, Charlson Comorbidity Index ≥7, other catastrophic illnesses, lack of multidisciplinary team involvement, and treatment in a low volume center. From these results, we advise that the DTI for all CRC patients, regardless of cancer staging, should be 30 days or less.