With a population in which 70% of the patients were overweight or obese, we reviewed retrospectively 135 breasts of 70 consecutive patients who underwent implant-based immediate breast reconstruction using freeze-dried AlloDerm as the acellular dermal matrix. Several obesity-related parameters were evaluated to determine their possible correlation to early postoperative complications. We found that breast width and surface area of AlloDerm usage correlated with the development of infection and mastectomy skin flap necrosis. Increased breast width and size of AlloDerm matrix implanted were correlated with higher rates of both minor and significant skin necrosis and of cellulitis. Body mass index was correlated with the development of cellulitis and minor and major skin necrosis but not with seroma or reconstruction failure. Preexisting breast cup size correlated with the development of seroma but not the other complications. We observed no statistically significant association between reconstruction failure and any of the parameters reviewed, but this is likely due to the small number of failures in our data set (n = 10).