Background: The CARMA1-BCL10-MALT1 (CBM) complex bridges T cell receptor (TCR) signaling to the canonical I kappa B kinase (IKK)/NF-kappa B pathway. The CBM complex constitutes a signaling cluster of more than 1 Mio Dalton. Little is known about factors that facilitate the rapid assembly and maintenance of this dynamic higher order complex. Findings: Here, we report the novel interaction of the aryl hydrocarbon receptor (AHR) interacting protein (AIP) and the molecular scaffold protein CARMA1. In T cells, transient binding of CARMA1 and AIP enhanced formation of the CBM complex. Thereby, AIP promoted optimal IKK/NF-kappa B signaling and IL-2 production in response to TCR/CD28 co-stimulation. Conclusions: Our data demonstrate that AIP acts as a positive regulator of NF-kappa B signaling upon T cell activation.