Emotional intelligence (EI) and transformational leadership (TL) have been identified as key factors in team effectiveness (TE); however, the empirical evidence remains fragmented and exhibits substantial conceptual and methodological heterogeneity, particularly in studies that simultaneously integrate these three variables. To address this gap, the present study examined the relationships among TL, EI, and TE by applying the PRISMA 2020 protocol and the PICO-S framework. A total of 728 studies published in Scopus, Web of Science, ScienceDirect, Emerald, ProQuest, and APA PsycNet were identified, of which 22 studies were included in the systematic review and 15 documents in the meta-analysis. The results revealed positive and statistically significant correlations between TL–TE (9 studies, 18 effects, N = 3480; r ≈ 0.45), EI–TE (8 studies, 15 effects, N = 3440; r ≈ 0.41), and EI–TL (4 studies, 6 effects, N = 1955; r ≈ 0.63), with effect sizes and levels of heterogeneity ranging from moderate to high. Additionally, variations in the strength of these relationships were observed according to sample size, year of publication, and methodological quality. In conclusion, EI emerges as a central resource that strengthens TL and, through psychological and relational mechanisms, consistently enhances TE in complex organizational contexts.