The use of neoadjuvant chemotherapy followed by tumor reduction surgery, also called interval debulking surgery (IDS), is considered an alternative therapeutic regimen for selected patients with advanced stage epithelial ovarian cancer (EOC). Although minimal residual disease has been proven to be a prognostic factor in traditional cytoreduction for advanced stage EOC, predictive factors after IDS still remain unexplored. The aim of this study was to determine the prognostic value of post-neoadjuvant histologic changes with clinical outcome. Three pathologists evaluated 67 cases for the following parameters: fibrosis, necrosis, residual tumor, and inflammation. The Cohen's kappa statistic was used to measure agreement among pathologists. Univariate and multivariate Cox proportional hazards models were used to determine the association between histologic parameters and recurrence-free survival (RFS) and overall survival (OS). There was substantial to almost perfect agreement among the three pathologists in all four histologic parameters (k ranged from 0.65 to 0.97). Fibrosis was associated with longer RFS (P = 0.0257) with a median of 20 months for tumors with fibrosis (3+) versus 12 months for tumors with fibrosis (1+, 2+) and longer OS (P = 0.0249) with a median of 51 months for tumors with fibrosis (3+) versus 32 months for tumors with fibrosis (1+, 2+). Our results revealed that patients with tumors exhibiting fibrosis (1+, 2+), as well as necrosis (0, 1+), had significant shorter RFS and OS (P = 0.059 and P = 0.0234, respectively). We suggest that the assessment of fibrosis and necrosis should be implemented in pathologic evaluation and prospectively validated in future studies.