The temperament of dairy cows interferes in milk yield and quality, but there is a lack of consensus throughout the literature. Thus, systematic review (SR) and meta-analysis (MA) methodologies were used to assess the effects of dairy cow temperament on milk yield. Our literature search included four electronic databases (CABI Abstracts, Web of Science, PubMed, and Scopus) and bibliographies of the publications included on MA. As inclusion criteria, we considered publications about the temperament of lactating cows and its effect on daily milk yield and total milk yield (whole lactation). A random effect-MA was carried out separately for daily milk yield and total milk yield related to each class of cows? temperament, 'low' (low reactivity, calm animals), 'intermediate' (intermediate reactivity), and 'high' (high reactivity, reactive animals). © The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved.