Introduction Systemic lupus erythematosus (SLE) is a connective tissue disease that is chronic, recurrent and multisystem with unknown aetiology. There is still no single biomarker that is pathognomonic for the disease. We know that platelets are the main part of haemostasis and thrombosis. We aimed to investigate whether there is a connection between MPV with SLE and inflammatory markers. Material and Methods We have included 39 female patients with SLE and 45 controls in this study. In both groups, erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP) levels and MPV levels were investigated. Clinical findings and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) were evaluated in patients. Results There was no significant difference between the two groups in terms of demographic data. The MPV was 8.1 +/- 0.5 (mean +/- SD) in the patient's group and 7.6 +/- 0.3 in the control group. There was a significant difference between the two groups in terms of MPV (P < .001). The ESR level was 30.7 +/- 29 in the patient's group and 16.7 +/- 10 in the control group. In the patient's group, the CRP levels were higher compared with that of the control group (8.2 +/- 13, 4.5 +/- 4, respectively). We found a statistically significant positive correlation between MPV with arthritis (r = .310,P = .004), nephritis (r = .446,P < .001), central nervous system involvement (r = .241,P = .027), vasculitis (r = .228,P = .037) and SLEDAI (r = .329,P = .002). In our study, we found increased levels of MPV in patients with SLE. Also, we observed a positive correlation among MPV with sedimentation, CRP, clinical manifestations and SLEDAI. Conclusion We consider that MPV may be a new activation indicator for the SLE.