Recent research on MALT1 (mucosa-associated-lymphoid-tissue lymphoma-translocation gene 1), a protein essential for nuclear factor-κB (NF-κB) activation, has uncovered new mechanisms by which MALT1 can orchestrate intracellular signalling events. Here, Margot Thome highlights recent progress which characterizes how the protease and scaffolding functions of MALT1 modulate T-cell activation.