The treatment of ankylosing spondylitis (AS) and psoriatic arthritis (PsA) positively changed since the introduction of anti-TNFα drugs. These treatments were shown to reduce the symptoms and signs of the diseases and improve the quality of life. However, a variable percentage of patients do not respond to anti-TNFα or can exhibit a loss of response and, furthermore, despite anti-TNFα drugs’ proven efficacy in reducing peripheral radiographic progression in PsA, the impact in reducing radiographic damage in AS is still debated. Recently, the discovery of new pathogenic mechanisms paved the way to the development of new drugs that target other pro-inflammatory cytokines. In particular, the inhibition of interleukin (IL)-17, which is the principal cytokine produced by Th17 lymphocytes, a pro-inflammatory subset involved in both inflammation and new bone formation in AS and PsA, demonstrated promising results. The new molecule secukinumab, an IL-17A inhibitor, showed its efficacy and safety in phase III randomized clinical trials in AS and PsA and is the first non-anti-TNFα biologic approved for the treatment of AS, providing a useful alternative treatment strategy in both diseases. The aim of this article was to review the pathophysiological basis, the efficacy and the safety of secukinumab treatment in AS and PsA patients.