Behçet's syndrome (BS) is a rare multisystem vasculitis involving blood vessels of any size. BS aetiology is still unclear to date, and the heterogeneity of clinical expression among ethnics and genders make early diagnosis challenging. However, so far, considerable efforts have been made toward the understanding of BS, leading researchers to agree that the coexistence of some environmental triggers and a genetical susceptibility both underlie BS aetiopathogenesis. In particular, viral agents, oral microbial flora, and mucosal microbiota have been widely explored in this regard, but still no specific microorganism has been definitely linked to the disease aetiology. Likewise, the concept that some environmental factors may play a role in BS clinical presentation has emerged based on the growing evidence that disease severity is usually higher in male patients, and that diet and fatigue may be involved in disease recurrence, especially in mucocutaneous manifestations. Moreover, smoke cessation is acknowledged as a risk factor for oral ulcerations, although the underlying mechanism is still not clear. All those environmental factors play their effects through epigenetic mechanisms. The aim of this review is to discuss the evidence on the role of environmental factors in BS aetiopathogenesis and clinical course.