Hidradenitis suppurativa (HS) is a chronic inflammatory disease with numerous cutaneous and systemic complications that can significantly impair patient quality of life and clinical outcomes. This chapter discusses both common and severe complications of HS, including sinus tract, contracture, and fistula formation; lymphedema; squamous cell carcinoma (SCC); anemia; renal dysfunction’ amyloidosis; and infection. Occlusion of hair follicles accompanied by recurrent inflammation and bacterial biofilms likely contribute to the pathogenesis of many of these complications, promoting persistent abscesses, scarring, and the formation of complex sinus tracts, perianal fistulas, and disfiguring tissue changes. Lymphedema, particularly in the anogenital region, can cause profound functional and psychosocial distress. SCC is a rare but potentially fatal complication of long-standing HS, especially in the gluteal and perineal regions. Systemically, HS is associated with anemia of chronic disease, renal impairment, and amyloid A amyloidosis, which may present with proteinuria or nephrotic syndrome. Additionally, HS patients are prone to skin and systemic infections due to immune dysregulation and impaired barrier function. We conclude that early recognition of complications and routine screening for systemic involvement are essential for mitigating morbidity and improving long-term outcomes in HS patients.