To characterize the interactomes of PEAK1 and PEAK2 homodimers, and the PEAK1/PEAK2 heterodimer, we applied bimolecular complementation affinity purification coupled with tandem mass spectrometry (BiCAP-MS/MS), a recently-developed technique that specifically identifies the interactors of any pair of interacting proteins while excluding those binding to individual components. Appropriate pairs of V1- and V2-tagged proteins were co-transfected into HEK293T cells, and then specific dimeric complexes were affinity purified with GFP-Trap nanobody and associated proteins identified by LC-MS/MS. Proteins exhibiting significantly increased abundance in particular PEAK dimers versus the Venus control were identified by label-free quantitative MS analysis, and are presented in volcano plots.