Objective: Ectopic pregnancy (EP) is the major cause of maternal morbidity and is responsible for maternal mortality in the first trimester. In order to reduce undesirable results, it is necessary to find rapid and accurate, non-surgical diagnostic tests for EP. The goal of the study was to investigate the differences in complete blood count parameters between tubal EPs and healthy pregnancies in be used in the diagnosis of ectopic pregnancy. Study design: White blood cell (WBC), neutrophil, monocyte, lymphocyte, platelet (PLT) counts, mean PLT volume (MPV) and PLT distribution width (PDW) levels in the complete blood count samples have been obtained from subjects with diagnosed tubal EP (n=78; study group) and women with healthy intrauterine gestations (n=79; control group). Statistical comparisons between groups were performed using the t test. Results: PDW levels were found to be significantly higher in the control group than EP (p<0.001). However, no differences between the study and control groups with regard to PLT and MPV levels were observed. WBC levels were found to be significantly higher in the EP group as compared to controls (p<0.001). When leukocyte differentials were compared, monocyte counts in the EP group were significantly higher than in controls (p=0.005). No statistically significant differences in neutrophil and lymphocyte values were observed in either group. Conclusion: PDW as an indicator of PLT activation is lower in tubal EP than intrauterine pregnancy so, possibly, endometrial invasion in the intrauterine pregnancy needs more PLT activation. Monocyte counts are higher in tubal EP, indicating that monocyte activation in the pathophysiology of EP could be effective in the formation of tubal motility and microenvironment regulation.