Background: Every year a lot of people are injured due to road traffic accidents. The majority of these injuries include long bone fractures, and the best treatment for these injuries is the surgical fixation with an intramedullary nail. Several complications have been described after intramedullary nailing of long bone fracture. However, one of the most common problems associated with tibia primarily, and retrograde femoral nailing secondarily, is chronic anterior knee pain. Objectives: To estimate the incidence and identify factors associated with knee pain intramedullary nailing for femur fracture in patients operated with a SIGN nail in TGSH& FHSH, Bahirdar, Amhara Region, Ethiopia February 1, 2020 to January 31, 2022. Methodology: Hospital based retrospective study was conducted on 110 patients who were admitted and operated with retrograde SIGN nail in TGSH& FHSH from February 1, 2020 to January 31, 2022 G.C who fulfill the inclusion criteria. Standardized format and tool was used to fill information from SIGN database, patents chart and patient phone interview. The collected data was entered into Epi Info version 7.2 and analyzed with SPSS version 26.0. Binary logistic regression model was used to analyze the association between variables. Finally tables, charts, graphs and other methods like percentile used to present and appraise results. Result: The overall occurrence of knee pains after retrograde SIGN nail is 36.4%. Severity and prevalence varies with fracture sites, screw penetration of medial cortex, time from injury to definitive surgery. Distal third Fracture [AOR=2.74, 95% CI (1.100-6.826], Prominent screw [OR=8.089, 95%CI (2¬¬.698-24.258)], Knee physiotherapy [OR= 0.395%CI (0.150-0.964)] were significantly associated with knee pain. Conclusion and Recommendation: Overall incidence of knee pain after retrograde SIGN nail for femur fracture was comparable to other similar studies. Distal third fracture, interlocking screws longer than the bone diameter and post-operative physiotherapy were factors significantly associated to post-operative knee pain after retrograde nail for femur fracture. Using properly measured screws and physiotherapy are highly recommended.