We retrospectively analysed 153 patients with metastatic colorectal cancer who received FOLFOX with or without bevacizumab as first-line chemotherapy. Several background characteristics and chemotherapy features (grade of neutropaenia, use of bevacizumab or irinotecan, re-introduction of FOLFOX, and tumour progression) as time-varying covariates were analysed as potential prognostic factors. Of the 153 patients, mild neutropaenia (grade 1-2) occurred in 60 patients (39%) and severe neutropaenia (grade 3-4) occurred in 46 patients (30%). The other 47 patients (31%) did not experience neutropaenia. According to a multivariate Cox model with time-varying covariates, hazard ratios (HRs) of death were 0.55 (95% confidence interval (CI), 0.31-0.98; P=0.044) for patients with mild neutropaenia and 0.35 (95% CI, 0.18-0.66; P=0.002) for those with severe neutropaenia. Both mild and severe neutropaenia during chemotherapy are associated with improved survival in patients with MCRC. Prospective trials are required to assess whether dosing adjustments based on neutropaenia may improve chemotherapy efficacy.