Species richness, defined as the number of species within a specific area, exhibits spatial variation at most spatial scales. The drivers behind these patterns, especially for marine invertebrates, remain a subject of ongoing debate. In this study, we explore the determinants of species richness for shallow-water gorgonians (Cnidaria: Anthozoa) in the Eastern Tropical Pacific, utilizing a comprehensive database of geographic occurrences and generalized linear mixed models analyses to investigate the influence of seven environmental variables in the context of four theoretical frameworks (Species-Energy, Environmental Heterogeneity, Climate Seasonality, and Past Climatic Stability hypotheses). Our methodology aims to account for potential spatial autocorrelation, enhancing the reliability of results. Our findings indicate a robust positive association between sea bottom temperature and species richness, supporting the Species-Energy hypothesis. Temperature, a key factor for marine biodiversity, likely enhances gorgonians’ metabolic, ecological, and mutation rates. Topographic ruggedness, climatic stability, and light availability were significant predictors of species richness, though their effects varied between subsets of analyzed taxa. Consequently, although our analysis supports the Environmental Heterogeneity and Past Climatic Stability hypotheses, their importance appears secondary. Overall, this research highlights the critical role of contemporary factors (predominantly temperature and topographic ruggedness) and historical factors, particularly climatic stability over the last 20,000 years, in influencing the distribution of gorgonian species richness in the Eastern Tropical Pacific.