Background: Femoral shaft fractures in adults are major long-bone injuries that commonly follow high-energy trauma and are associated with substantial morbidity, prolonged hospitalization, and clinically important complications. Objective: To determine the frequency, patterns, and predictors of complications among adults with femoral shaft fractures managed at Al-Kadhimiya Teaching Hospital and Imam Ali Hospital, Baghdad, Iraq. Methods: A hospital-based retrospective observational study was conducted from February 1, 2021 to June 30, 2025. Adults (≥18 years) with radiologically confirmed femoral shaft fractures and complete records were included; pathological and periprosthetic fractures and incomplete files were excluded. Data were extracted from admission logs, operative records, and radiology databases. Variables included demographics, injury mechanism, fracture characteristics (including AO/OTA classification), open/closed status, associated injuries, comorbidities (including smoking and diabetes), treatment modality, time to surgery, hospital course, and early/late complications. Standard radiographs were used to assess alignment and union. Results: A total of 312 patients were analyzed (mean age 36.8 ± 12.4 years); most were males (236; 75.64%) and urban residents (204; 65.38%). Road traffic accidents were the leading mechanism (182; 58.33%), followed by falls from height (71; 22.76%). Most fractures were closed (247; 79.17%), with a substantial proportion of open fractures (65; 20.83%). AO/OTA 32-B patterns predominated (131; 41.99%). Intramedullary nailing was the main treatment (208; 66.67%), and the mean time to surgery was 3.4 ± 1.9 days. Major complications included delayed union (36; 11.54%), surgical site infection (29; 9.29%), nonunion (21; 6.73%), malunion (18; 5.77%), and implant failure (15; 4.81%). Significant predictors of major complications were smoking (p=0.002), diabetes (p=0.004), open fractures (p<0.001), surgical delay >5 days (p<0.001), and associated injuries (p=0.011). Conclusion: Adult femoral shaft fractures in Baghdad predominantly affect young men and are primarily caused by road traffic trauma. Complications remain frequent and are strongly associated with modifiable patient factors (smoking, diabetes) and injury/management factors (open fractures, polytrauma, delayed surgery). Targeted prevention and optimized perioperative pathways focusing on early stabilization and risk-factor control may improve outcomes.