Purpose: The objective of this study was to assess the predictive role of the neutrophil/lymphocyte ratio (NLR) for invasion of gestational trophoblastic disease (GTD). Materials and Methods: A retrospective analysis was conducted on 127 women who were managed at our clinic for GTD. Of all patients, 8 showed invasion according to histological examination. The clinical parameters of patients with invasive GTD (Group 1; n=8) were compared with patients who showed no invasion (Group 2; n=119). All underwent a prior uterine evacuation and followed up by regular assessment of ${eta}$-hCG titers. Results: Demographic and obstetric history and pre-evacuation hCG levels of the patients showed no statistically significantly difference between the groups (p>0.05). The mean gestational weeks (GW), size of the GTD and NLR levels were statistically significantly higher in the invasive GTD group (p<0.05). Correlations between invasion and gestational weeks, size of GTD, post-evacuation chemotherapy and NLR were evident. ROC curve analysis demonstrated that GW, size of GTD and NLR may be discriminative parameters in predicting invasion of GTD. Conclusions: To the best of our knowledge, this is the first study evaluating the predictive role of NLR in invasion of GTD. In conclusion, we think that pretreatment NLR can be used as a biomarker of invasion in GTD.