This study aimed to identify the variables associated with fixation failure in intertrochanteric fractures treated with cephalomedullary nailing (CMN). We retrospectively analyzed 251 consecutive patients who underwent surgery between January 2016 and July 2019. In order to identify predictors of failure (cut-out, cut-through, and/or nonunion), we analyzed: gender, age, fracture stability (according to the AO/OTA Classification), femoral neck angle (FNA), FNA as compared to the contralateral hip, lag screw position, and tip-apex distance (TAD). The failure rate was 9.6%: there were 10 cut-outs (4%), 7 non-unions (2.8%), and 7 cut-throughs (2.8%). Univariate logistic regression analysis showed that the risk factors for fixation failure were: female sex (p= 0.018), FNA <125° (p= 0.003), a difference in FNA of 7.5° as compared to the contralateral hip on the lateral radiograph (p= <0.0001), superior (p= 0.0141) and anterior position (p= <0.0001) of the lag screw, and TAD >25mm (p= 0.016). According to the multivariate analysis, female gender (OR 12.92 ; p 0.0019), the difference in FNA on the lateral view (OR 1.36; p < 0.001), and the anterior position of the screw in the femoral head (OR14.01;p <0.001) were confirmed as independent predictors of failure. In order to avoid failures in intertrochanteric hip fractures treated with CMN, this study confirmed the importance of achieving an accurate reduction on the lateral plane and avoiding the anterior position of the screw on the femoral head.