Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterised by aberrant activation of innate and adaptive immune responses. Part of this hyper-activation is due to the interferon (IFN) system. Deregulated expression and activity of the type-I IFN system has been extensively studied in pSS. Type-III interferons (IFNs) are the latest addition to the IFN family, and exhibit potent anti-viral functions, similarly to type-I IFNs. More recently they have started to attract attention as key modulators in the interface of innate and adaptive immunity and chronic inflammation. Deregulated expression of type-III IFNs has been demonstrated in various autoimmune diseases over the last ten years. The scope of this review is to summarise recent findings regarding the biology of type-III IFNs in pSS. We highlight factors that regulate their induction, their downstream effects, their similarities and differences with type-I IFNs and their possible modes of action in Sjögren's syndrome. Finally, we discuss their potential benefits as targets for therapeutic intervention.