Although social-emotional skills are more malleable than cognitive skills and have potential benefits for a range of academic and life outcomes, previous studies on the topic have suffered from many issues (e.g., consideration of only a small subset of skills, single-informant and single-cohort design). To address these limitations, this study used a multi-informant (self, teacher, and parent) and multi-cohort (ages 10 and 15 from Finland, N = 5,533) perspective to study the association between social-emotional skills and 20 educational (e.g., school grades and engagement), psychological (e.g., life satisfaction, social relationships), and health outcomes (e.g., eating habits, sleep trouble). Results showed that (a) there was a modest level of inter-rater agreement on social-emotional skills, with the highest agreement between students and parents (mean r = .41); (b) inclusion of multi-informant ratings substantially enhanced the ability of social-emotional skills in predicting outcome variables, with parent- and self-rated skills playing important, unique roles; (c) by modeling skills at the facet-level rather than at the domain-level, we identified the key skills for different outcomes and found significant variation in facets’ predictive utility even within the same domain; (d) although the old cohort showed lower levels of most social-emotional skills (9/15), there were only very minor changes in the inter-rater agreement and predictive utility on outcomes. Overall, Self-Control, Optimism, Trust, and Energy were found among the four most important skills for academic and life success. We further identifed unique contribution of each skill for certain outcomes, which points the way to effective and precise interventions.