Dipeptidyl peptidase 9 (DPP9) is an amino peptidase with the unusual ability to cleave a peptide bond post-proline. Its function affects immunity, DNA-repair, cell signaling, memory and neonatal survival; its dysregulation is linked to cancer and immune-related disorders. While most studies focus on its canonical catalytic function, scaffolding functions of DPP9 are just beginning to emerge. To define the interactome of DPP9, we used TurboID-based proximity labeling in DPP9 HEK293 knock-out cells reconstituted with doxycycline-inducible miniTurboID–DPP9.