We hypothesized that mean platelet volume (MPV), a reliable marker of platelet activation, might be elevated in primary Raynaud's phenomenon (PRP) even if there was no thrombotic complication in our subjects. In this retrospective-cohort study, we examined the clinical value of MPV in 200 patients with PRP and 116 clinical controls, and measured MPV and platelet P-selectin (CD62P) in all study participants. We also evaluated the effect of age, gender, and disease duration on these platelet activation markers in PRP. MPV and CD62 positivities were significantly (p<0.001) elevated in patients with PRP compared with controls. These differences retained when patients and controls were analyzed according to age, gender, and the disease duration. In logistic regression analysis, MPV (OR: 15.8, 95% CI: 8.14-30.64, p<0.001) and CD62P (OR: 11.3, 95% CI: 4.85-26.12, p<0.001) were found to be independently associated with PRP. In conclusion, increased MPV is independently related to PRP, and its level was not influenced by age, gender, and the duration of PRP.