Increased number of overweight and obese women are seeking breast reconstruction. Studies have demonstrated that obese experience increased rates of complications, but less data is available considering overweight patients. We analyzed the impact of body mass index (BMI) on perioperative characteristics and complications in unilateral delayed deep inferior epigastric perforator flap (DIEP) reconstructions. The records of patients with DIEP reconstruction performed between 2014 and 2020, were retrospectively analyzed. Patients were categorized into obese (BMI ≥30), overweight (BMI 25.0–29.9), and normal-weight groups (BMI <25). Patient characteristics (age, comorbidity, radiation, abdominal surgery, ASA category, and smoking), perioperative characteristics (length of operation, blood loss, vasoactive drugs, fluid administration, and urine output), and postoperative complications were recorded. The study included 308 patients. Of these, 104 (34%) were normal-weighted, 142 (46%) overweight and 62 (20%) obese. Among patients with BMI ≥ 25, blood loss increased (p = 0.002) and the length of operation tended to be longer (p = 0.072). No between-groups difference existed in fluid administration (p = 0.319), urine output (p = 0.425), or use of vasoactive drugs (p = 0.815). There was no statistically significant difference in overall complications (p = 0.122) between BMI groups. Blood loss >150ml was associated with both minor and major complications (p = 0.022). Greater BMI moderated with the radiation therapy for higher risk of minor complications (OR 42.0, 95%CI 3.54–49.7, p = 0.003). We conclude that greater BMI alone is not associated with a higher overall complication rate, but both overweight and obesity may be moderators for other risk factors.