Attachment security priming has important theoretical and practical implications. We review security priming theory and research and the recent concerns raised regarding priming. We then report the results of a meta-analysis of 120 studies ( N = 18,949) across 97 published and unpublished articles (initial pool was 1,642 articles) investigating the affective, cognitive, and behavioral effects of security priming. A large overall positive effect size ( d = .51, p < .001) was found across all affective, cognitive, and behavioral domains. The largest effect was found for affect-related outcomes ( d =.62, p < .001), followed by behavioral ( d = .44, p < .001), and cognitive ( d = .45, p < .001). Trait attachment anxiety and avoidance moderated the effects of subliminal security priming for behavioral outcomes—security priming effects were larger among people higher on attachment anxiety and avoidance. Assessment of publication bias revealed mixed evidence for the possible presence of asymmetry.