Neuroendocrine tumors (NETs) are a heterogeneous group of epithelial neoplasms with predominantly neural and endocrine differentiation that have the ability to produce peptide hormones and other biologically active substances. The histologic characterization of NETs based on differentiation and grading is crucial to determining prognosis and treatment. Surgery still offers the best chance of cure for patients with NETs, and tumor resection is the preferred approach when possible. For locally advanced or metastatic disease, approaches to treatment can vary widely depending on the extent of disease and goals of therapy. A better understanding of the biology of NETs acquired over the last decade has facilitated the development of targeted therapies, such as everolimus and a variety of tyrosine kinase inhibitors. Furthermore, the field of theranostics has led to dramatic improvements in our diagnostic and treatment abilities. Chemotherapy has a role in the treatment of NETs, evidenced by the benefit shown with the combination of temozolomide and capecitabine to treat pancreatic NETs. Somatostatin analogues are a mainstay of treatment because they reduce secretory products and have antiproliferative effects on NET cells. In this work, we aim to review the landscape for the diagnosis and treatment of well-differentiated NETs.