This paper characterises complex predicates and light verb constructions in Modern Irish. Light verbs are attested in many of the world’s languages (Alsina, Bresnan & Sells, 2001; Butt, 1995, 2003). Cross linguistically, there appears to be a common class of verbs involved in these constructions and generally there is agreement that light verbs contribute to the formation of complex predicates. Light verbs seem have a non-light or ‘heavy’ verb counterpart. In this paper we discuss the light verb constructions (LVC) as found in modern Irish and how they form complex predicates. We claim that the light verb (LV) encodes the event process initiation (or cause) and the matrix verb indicates the bounded component or result. In light verb constructions, the matrix verb appears in Modern Irish syntax as a verbal-noun form. The function of light verbs in these constructions is to modulate the event and sub-event semantics. We distinguish between auxiliary verbs constructions (AVC) and those constructions involving complex predicated and light verbs (Aikhenvald & Dixon, 2006; Anderson, 2006). We provide evidence based on an analysis of Irish data that shows how aspect and argument structure considerations are resolved for the complex predicate within the light verb construction via the linking system between semantics and syntax. We motivate a functional account, based on Role and Reference Grammar (Nolan, 2012; Nolan & Diedrichsen, 2013; Van Valin, 2005; Van Valin & LaPolla, 1997), that appeals to the analysis of complex predicates within a consideration of the layered structure of the clause.