In contrast to rheumatoid arthritis, in psoriatic arthritis (PsA), the efficacy of disease-modifying antirheumatic drugs (DMARDs) combination has not been documented. We conducted a retrospective study to evaluate the effectiveness of leflunomide (LEF) addition in 11 PsA patients with articular manifestations that failed to respond to methotrexate (MTX) monotherapy [disease activity score in 28 joints (DAS28) > 3.2)]. Eight of them, all with moderate disease activity (DAS28 < 5.1) at baseline, tolerated the combination. A statistically significant improvement of the mean DAS28, based on erythrocyte sedimentation rate (ESR), and its variables, and C-reactive protein (CRP) at 12-16 weeks after LEF addition was observed. Mean change of DAS28 in patients with polyarticular disease did not differ compared with those with oligoarticular. Based on the European League Against Rheumatism (EULAR) response criteria, none of our patients achieved a good response, seven had a moderate response, and one was a non-responder. The two patients with the lower DAS28 at baseline attained low disease activity (LDA, DAS28 ≤ 3.2), while none reached remission (DAS28 ≤ 2.6). Achievement of clinical remission or at least LDA has been recently proposed as the goal of treatment in PsA. Our results imply that LEF addition may serve as an alternative therapeutic modality for patients with moderately active PsA and, as lower as possible, residual disease activity after the initial therapy with MTX alone.