The purpose of this study is to identify any association between malnutrition and morbid obesity and determine if either independently increases complications following primary total joint arthroplasty (TJA). The study retrospectively reviewed a series of 670 patients who underwent primary TJA at a single institution. Patients were categorized as malnourished if their preoperative serum albumin was <3.5 mg/dL and morbidly obese if their body mass index was >40 kg/m(2). Of the 670 patients in the study, 83 patients were malnourished (12.4%), while 125 patients (18.7%) were morbidly obese. Morbidly obese patients were more likely to be malnourished than nonmorbidly obese patients (19% vs. 11%, p = .010). Malnutrition is an independent risk factor for complications [adjusted odds ratio (OR) 3.00, 95% confidence interval (CI) 1.56-5.75]. Morbid obesity was not independently associated with a significant increase (adjusted OR 1.82, 95% CI 0.70-4.71). Preoperative screening with serum albumin, particularly in morbidly obese patients, can identify at-risk patients for complications.