Evolutionary theory predicts that assortative mating – the tendency of similar individuals to mate with each other – plays a key role for speciation by generating reproductive isolation between diverging populations. However, comprehensive tests for an effect of assortative mating on species richness at the macro-evolutionary scale are lacking. We used a meta-analytic approach to test the hypothesis that the strength of assortative mating is positively related to species richness across a broad range of animal taxa. Specifically, we ran a phylogenetically independent meta-analysis using an extensive database of 1447 effect sizes for the strength of assortative mating measured within populations, encompassing 307 species from 130 families and 14 classes. Our results suggest that there is no relationship between the strength of assortative mating and species richness across and within major taxonomic groups and trait categories. Moreover, our analysis confirms an earlier finding that animals typically mate assortatively (global effect size r = 0.36; 95% confidence limits: 0.19 − 0.52) when accounting for phylogenetic non-independence. In conclusion, we argue that future advances will rely on a better understanding of the evolutionary causes and consequences of the observed intra- and interspecific variation in the strength of assortative mating.