There is great variability in methodological quality assessment (MQ) systematic reviews (SRs). We identified how MQ assessment in SRs that included observational studies in Health Science is applied and explored associated characteristics. A search was conducted in PubMed and five trained reviewers randomly selected 1,025 references after sample size calculation. Only SR published in English (September 2019/2020) were included. Selection and data extraction were conducted in two phases. Data were analyzed descriptively and using logistic regressions. After eligibility criteria application, 205 SRs were included. Only 27.8% informed the protocol registration and 80.0% described having followed a reporting guideline. Proportion’ SRs did not seem to present MQ assessment (OR 4.22; 95% CI: 1.38-12.87; P =0.01). SRs that did not register the study protocol (9.70; 95% CI: 1.95-48.27; P 0.001), those that did not inform the included study design (5.96; 95% CI: 1.63-21.77; P 0.001) and those without MA (OR 8.90; 95% CI: 2.79-28.43; p0.001) increased the odds of not evaluating MQ. Newcastle-Ottawa (47.5%), Joanna Briggs Institute (8.2%) and National Institute of Health (7.1%) were the most commonly used MQ tools. Lack of protocol registration, absence of information about the design of included studies, absence of MA, and proportion’ SRs were associated with lack of MQ assessment.