In humans, high Notch activation promotes gamma delta T cell development, whereas lower levels promote alpha beta-lineage differentiation. How these different Notch signals are generated has remained unclear. We show that differential Notch receptor-ligand interactions mediate this process. Whereas Delta-like 4 supports both TCR-alpha beta and -gamma delta development, Jagged1 induces mainly alpha beta-lineage differentiation. In contrast, Jagged2-mediated Notch activation primarily results in gamma delta T cell development and represses alpha beta-lineage differentiation by inhibiting TCR-beta formation. Consistently, TCR-alpha beta T cell development is rescued through transduction of a TCR-beta transgene. Jagged2 induces the strongest Notch signal through interactions with both Notch1 and Notch3, whereas Delta-like 4 primarily binds Notch1. In agreement, Notch3 is a stronger Notch activator and only supports gamma delta T cell development, whereas Notch1 is a weaker activator supporting both TCR-alpha beta and -gamma delta development. Fetal thymus organ cultures in JAG2-deficient thymic lobes or with Notch3-blocking antibodies confirm the importance of Jagged2/Notch3 signaling in human TCR-gamma delta differentiation. Our findings reveal that differential Notch receptor-ligand interactions mediate human TCR-alpha beta and -gamma delta T cell differentiation and provide a mechanistic insight into the high Notch dependency of human gamma delta T cell development.