BACKGROUND The optimal timing to definitive osteosynthesis in the polytraumatized patient remains an unanswered question. Early total care, damage control orthopaedics, and early appropriate care have been described to manage the fractures in these patients, but there is a paucity of literature specific to ipsilateral tibial and femoral fractures. We sought the perioperative outcomes of primary simultaneous intramedullary nailing (IMN) versus temporizing external fixation (EF) of both fractures. METHODS A chart review of all patients who sustained fractures of the ipsilateral femur and tibia that were definitively treated with (IMN) from January 2010 to December 2020 was performed. Patients who underwent initial EF and those that were primarily treated with IMNs were examined. RESULTS IMNs and EF were the initial treatment in 23 and 16 patients, respectively. The mean (range) injury severity score (ISS) was 23.3 (33) in the EF group vs. 18.5 (34) in the IMN group, (p = 0.0686). The EF group had a higher total transfused units of packed red blood cells 7.4 vs. 2.8, the mean initial operative time was 236 vs. 282.6 (min), (p = 0.7399), a longer mean total operative time 601.78 vs. 236 (min), and longer mean length of stay 15.6 vs. 11 (days), (p < 0.5). Rates of complications were not significantly different between groups. CONCLUSIONS Primary IMN is as safe as provisional EF in the adequately resuscitated patient with ipsilateral femoral and tibial fractures. This implies the fixation of both fractures into a single surgery without increasing perioperative complications, and decreasing total hospital stay in patients with sufficient preoperative resuscitation.