Immigrants represent a numerous, and substantially underserved, community of over 44 million people in the U.S., including 700,000 recipients of the Deferred Action for Childhood Arrivals (DACA) program (Batalova et al., 2020). Opportunities for competency training in professional psychology to serve this community, however, are scarce, both within doctoral training programs and professional development contexts (American Psychological Association [APA], 2012; Benuto et al., 2018). This article reports the results of a study assessing the impact of a 3-part web-based training series that targeted several Foundational and Functional Competency Domains as outlined by Fouad et al. (2009). Pretest assessments of 1,327 participants revealed limitations in the domains of knowledge and awareness of cultural competencies for working with immigrants. Those who completed the posttest assessments following each of the three Webinars showed significant increases in competency domains based on paired-sample t-tests. Repeated measures mixed-design analyses of variance tested the moderating effects of demographic characteristics (i.e., race, ethnicity, gender), level of training, career stage, or prior experience working with immigrants on these increases in cultural competence. Results provide valuable information regarding targeted subgroups within the larger sample. Subsequent follow-up assessments on a narrower number of participants supported the continuing impact of the trainings over time. Results are discussed in relation to the critical role of evidence-based training that targets immigrant populations in the midst of global sociopolitical and immigration challenges, and how these may inform competency training in a graduate program and professional development contexts.