Insulin resistance, a key feature of type 2 diabetes, is an independent risk factor for developing cardiovascular diseases (CVD), and represents the core of metabolic syndrome (MetS). Actually, an intriguing correlation between MetS and inflammation associated with rheumatoid arthritis (RA) is largely accepted but not yet completely clarified in detail. Recently, the therapeutic arsenal against RA has been enriched of abatacept, a fusion protein (CTLA4 immunoglobulin) designed to modulate the T cell co-stimulatory signal mediated through the CD28-CD80/86 pathway. Here, we report a case of dramatic improvement in insulin resistance, estimated with the surrogate measure HOMA-IR, after treatment with abatacept. Lastly, we shortly review the preclinical evidences supporting a possible role of T lymphocytes in rheumatoid arthritis-associated insulin resistance and how abatacept could improve glucose metabolism by suppressing adipose tissue infiltrating cells.