Mailed outreach promoting colorectal cancer (CRC) screening with a stool blood test kit may increase participation, but magnitude and consistency of benefit of this intervention strategy is uncertain. Our aim was to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing mailed outreach offering stool tests to usual care, clinic-based screening offers on CRC screening uptake in the USA. We performed a systematic literature search of five databases for RCTs of mailed outreach from January 1980 through June 2017. Primary outcome was screening completion, summarized using random-effects meta-analysis as pooled differences in proportion completing the screening and relative risk of achieving screening compared to control. Subgroup analyses by test type offered-fecal immunochemical test (FIT) or guaiac fecal occult blood test (gFOBT), the presence of telephone reminders, and the presence of predominant underserved/minority population within study were performed. Quality of evidence was evaluated using the GRADE framework. Seven RCTs which enrolled 12,501 subjects were included (n = 5703 assigned mailed outreach and n = 6798 usual care). Mailed outreach resulted in a 28% absolute (95% CI 25-30%; I ² = 47%) and a 2.8-fold relative (RR 2.65, 95% CI 2.03-3.45; I ² = 92%) increase in screening completion compared to usual care, with a number needed to invite estimated to be 3.6. Similar outcomes were observed across subgroups. Overall body of evidence was at moderate quality. Mailed outreach offering a gFOBT or FIT is associated with a large and consistent increase in CRC screening completion and should be considered for more widespread implementation for improving screening rates nationwide.