Psoriatic arthritis (PsA) is an inflammatory disease in which specific immune cells, called T helper (Th) cells, play an important role. IL‑23 drives inflammation in PsA, and treatments that block IL‑23 are effective for many patients. Most research has focused on IL‑23’s effects on Th17 cells, but a related cell type, Th17.1, may also contribute to disease and is less well understood. In this study, we examined how IL‑23 affects human Th17.1 cells. We found that IL‑23 increases their inflammatory activity, while IL‑23 blockade reduces it, even when monocytes enhance their inflammatory state. These findings help explain why IL‑23 inhibitors are effective in PsA and highlight that Th17.1 cells may be important treatment targets.