TANK-binding kinase 1 (TBK1) was identified as a putative binding partner for optineurin (OPTN, also called NRP for NEMO-related protein) in two separate yeast two-hybrid screens using OPTN as bait. An interaction between OPTN and TBK1 was confirmed by co-transfection experiments in HEK 293 cells and by co-immunoprecipitation of endogenous OPTN and TBK1 from extracts of untransfected cells. A TBK1 binding site was identified in the N-terminal 127 amino acid residues of OPTN, the amino acid sequence surrounding residues 78–121 displaying striking homology to the TBK1-binding domains of the other three known binding partners for TBK1, namely TANK, NAP1 and SINTBAD. The OPTN binding domain in TBK1 was localised to the C-terminal 128 residues of TBK1 (residues 601–729) and TBK1[1–688] lacking the C-terminal 40 residues of TBK1, which cannot bind to TANK, was also unable to interact with OPTN. These findings demonstrate that OPTN interacts with TBK1 in a similar manner to TANK, NAP1 and SINTBAD. The OPTN[E50K] mutant, which is associated with a form of primary open angle glaucoma in man displayed strikingly enhanced binding to TBK1, raising the possibility that this interaction may underlie or contribute to familial POAG associated with this OPTN mutation.