Introduction: Due to improvements in our understanding of the pathogenesis of systemic lupus erythematosus (SLE), several target drugs have been and are being developed. One of the possible targets in SLE is co-stimulation between antigen-presenting cells and T cells. Abatacept is a co-stimulation moderator approved for the treatment of several autoimmune diseases. There is an unmet need for drugs with a better efficacy and safety profile when treating patients with SLE.Areas covered: In this review, the authors discuss the mechanism of action of abatacept including its role in the immune system and glomeruli, and relevant information about its clinical efficacy and safety. Possible explanations for the failure of previous randomized clinical trials are also discussed.Expert opinion: Abatacept has demonstrated efficacy in other autoimmune diseases, but in SLE, randomized clinical trials have failed to achieve their primary outcome. Despite these disappointing results and based on its mechanism of action, abatacept seems to have a role in lupus nephritis and arthritis. This should be corroborated with new trials which hopefully will overcome the design pitfalls of the ones conducted to date.