Data sources PubMed, EMBASE, Web of Science and Scopus. Study selection Randomised controlled clinical trials, cohort studies, case-control studies and case series reporting data on dental implant failures related to smoking published up to January 2019 were included, with no language restrictions. Data extraction and synthesis Data was extracted by one reviewer and quality assessment of the included observational studies was performed using the Newcastle-Ottawa scale. Smoker subgroups were categorised by number of cigarettes smoked daily, and statistical heterogeneities were assessed using Cochran's Q statistics and quantified using the I² test. Results A higher implant failure rate was found in patients who smoked <10 cigarettes/day than in non-smokers (p = 0.046), 95% CI (1-1.64). Likewise, patients who smoked >10 cigarettes/day showed higher failure rates than those smoking <10 cigarettes/day (p <0.001), 95% CI (1.31-2.17). Conclusions Increase in smoking dose appears to correspond directly with increase in implant failure rate. Smoking <10 cigarettes/day can be recommended as a safe level for dental implant failure.