Abstract Background Bevacizumab has an important role in first-line treatment of metastatic colorectal cancer. However, clinical trials studying its effect have involved distinct chemotherapy regimens with divergent results. The aim of this meta-analysis is to gather current data and evaluate not only the efficacy of bevacizumab, but also the impact of divergent backbone regimens. Methods A wide search of randomized clinical trials using bevacizumab in first-line metastatic colorectal cancer was performed in Embase, MEDLINE, LILACS and Cochrane databases. Meeting presentations and abstracts were also investigated. The resulting data were examined and included in the meta-analysis according to the type of regimen. Results Six trials, totaling 3060 patients, were analyzed. There was an advantage to using bevacizumab for overall survival (OS) and progression-free survival (PFS) (HR = 0.84; CI: 0.77-0.91; P < 0.00001 and HR = 0.72; CI: 0.66-0.78; P < 0.00001, respectively). However, heterogeneity of results was very high for both outcomes, and subgroup analyses supported the OS advantage with bevacizumab restricted to irinotecan-based regimens. Infusional fluorouracil subsets involved a minor proportion, and did not demonstrate statistical benefit in PFS or OS. Regarding toxicity, higher rates of grades 3-4 hypertension, bleeding, thromboembolic events and proteinuria were uniformly observed with bevacizumab, leading to increased treatment interruptions (HR = 1.47; P = 0.0004). Conclusions Bevacizumab has efficacy in first-line treatment of advanced colorectal cancer, but the current data are insufficient to support efficacy in all regimens, especially infusional fluorouracil regimens, like FOLFIRI and FOLFOX.