Single leg squat (SLS) is a common tool used in clinical examination to set and evaluate rehabilitation goals, but also to assess lower extremity function in active people. Objectives To conduct a review and meta-analysis on the inter-rater and intrarater reliability of the SLS, including the lateral step-down (LSD) and forward step-down (FSD) tests. Design Review with meta-analysis. Data sources CINAHL, Cochrane Library, Embase, Medline (OVID) and Web of Science was searched up until December 2018. Eligibility criteria Studies were eligible for inclusion if they were methodological studies which assessed the inter-rater and/or intrarater reliability of the SLS, FSD and LSD through observation of movement quality. Results Thirty-one studies were included. The reliability varied largely between studies (inter-rater: kappa/intraclass correlation coefficients (ICC) = 0.00-0.95; intrarater: kappa/ICC = 0.13-1.00), but most of the studies reached ’moderate’ measures of agreement. The pooled results of ICC/kappa showed a ’moderate’ agreement for inter-rater reliability, 0.58 (95% CI 0.50 to 0.65), and a ’substantial’ agreement for intrarater reliability, 0.68 (95% CI 0.60 to 0.74). Subgroup analyses showed a higher pooled agreement for inter-rater reliability of ≤3-point rating scales while no difference was found for different numbers of segmental assessments. Conclusion Our findings indicate that the SLS test including the FSD and LSD tests can be suitable for clinical use regardless of number of observed segments and particularly with a ≤3-point rating scale. Since most of the included studies were affected with some form of methodological bias, our findings must be interpreted with caution. PROSPERO registration number CRD42018077822. © Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.