Early definitive fixation (≤ 24 h) is preferred over delayed definitive fixation (>24 h) for patients with bilateral femur shaft fractures when accounting for age, sex, injury characteristics, additional fractures and interventions, and hospital level. Although mortality does not differ, overall morbidity and deep venous thrombosis rates, and length of hospital and intensive care unit stay are significantly lower. When early definitive fixation is not possible, early staged repair seems preferable over delayed definitive fixation.