Cohort studies are a type of observational study that follows samples of at-risk individuals forward in time to examine associations between measured exposures and future outcomes. Cohort studies have an essential role in evidence-based surgery. Cohort studies are the optimal study design to evaluate prognostic factors, allowing for efficient longitudinal follow-up of large, representative study samples. Cohort studies are also invaluable for the study of multiple exposures, rare exposures, exposures with known risks to which it would be unethical to allocate study participants, or in situations where there is a long interval of time between exposure and outcome. We present a practical guide for the appraisal of cohort studies in surgery. Our aim is to provide practicing surgeons and trainees with a framework for the evaluation of the methodological quality and applicability of cohort studies.