Preprints in the life sciences are gaining popularity, but release of a preprint still precedes only a fraction of peer-reviewed publications. Quantitative evidence on the relationship between preprints and article-level metrics of peer-reviewed research remains limited. We examined whether having a preprint on bioRxiv.org was associated with the Altmetric Attention Score and number of citations of the corresponding peer-reviewed article. We integrated data from PubMed, CrossRef, Altmetric, and Rxivist (a collection of bioRxiv metadata). For each of 26 journals (comprising a total of 46,451 articles and 3,817 preprints), we used log-linear regression, adjusted for publication date and scientific subfield, to estimate fold-changes of Attention Score and citations between articles with and without a preprint. We also performed meta-regression of the fold-changes on journal-level characteristics. By random effects meta-analysis across journals, releasing a preprint was associated with a 1.53 times higher Attention Score + 1 (95% CI 1.42 to 1.65) and 1.31 times more citations + 1 (95% CI 1.24 to 1.38) of the peer-reviewed article. Journals with larger fold-changes of Attention Score tended to have lower impact factors and lower percentages of articles released as preprints. In contrast, a journal’s fold-change of citations was not associated with impact factor, percentage of articles released as preprints, or access model. The findings from this observational study can help researchers and publishers make informed decisions about how to incorporate preprints into their work.