Purpose. To investigate the role of thrombocyte parameters in retinopathy of prematurity (ROP) development. Materials and Methods. This retrospective study included 120 preterm infants in total. Group 1 was formed by infants who developed type-1 ROP and received treatment. Group 2 was formed by infants who developed ROP and were not treated for ROP. Infants who did not develop ROP and whose retinal vascularization was completed in their follow-up formed Group 3. Gestational age, birth weight, and genders of groups were recorded. Platelet (PLT) count, mean platelet volume (MPV), and platelet distribution width (PDW) values were obtained from complete blood count. Platelet mass index (PMI) was calculated by multiplying the PLT count by MPV value. Thrombocytopenia was defined as PLT count mu L. All parameters were compared between the groups. Results. There were 40 preterm infants in each group. The mean PLT count was 272.43 +/- 122.67 in Group 1, 333.32 +/- 133.06 in Group 2, and 310.03 +/- 119.41 in Group 3. The difference in PLT count between the groups was not significant p=0.094. Thrombocytopenia was observed in 25% of Group 1, 10% of Group 2, and 10% of Group 3 p=0.095. No statistically significant difference was found in terms of MPV, PDW, and PMI values between the groups (p=0.102, p=0.097, and p=0.298, respectively). Conclusions. Although PLT count was lower and thrombocytopenia rate was higher in the type-1 ROP group, the differences were not found to be significant. Further prospective studies are required to evaluate the role of thrombocytes in ROP pathogenesis.