Obesity and the corresponding burden of related diseases is a major public health issue worldwide that is reaching pandemic proportions. Bariatric surgery is the only intervention that has been shown to result in substantial and lasting weight loss, and a decrease in overall mortality for patients with severe obesity. Consequently, the population of patients having undergone this procedure is increasing. Multifactorial weight-dependent and independent mechanisms underlying metabolic diseases could also drive preventable, but potentially life-threatening, long-term nutritional complications. However, given post-bariatric patients are prone to functional gastrointestinal symptoms and substantial weight loss, nutritional complications might be challenging. This Review is focused on the prevention and treatment of nutritional complications after bariatric surgery in the clinical setting.