Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease that presents as painful, deep-seated nodules, sinus tracts, and abscesses in about 1% of the population. Although the pathogenesis of HS is not perfectly understood, it is generally recognized to be caused by a combination of genetic, endocrine, environmental, and microbiological factors. The treatment principles of HS focus on decreasing the microbial load with antibiotics and/or modulating the host immune response to reduce inflammation. The treatment of adults with moderate-to-severe HS has significantly changed recently with the development of new biological medications and immunomodulators. While previously the mainstay of treatment of moderate-to-severe HS was adalimumab, a biologic tumour necrosis factor α inhibitor, the evidence for the use of other treatment classes such as interleukin (IL)-17 inhibitors, IL-1 inhibitors, and Janus kinase inhibitors has been growing. The goal of this review article is to review the available evidence that supports the efficacy and safety of biologics and small molecule immunomodulator treatments to treat adults with moderate-to-severe HS.