An argumentative text should present evidence that prove the author’s claims, which implies logical organization of the text and expression of a cause-and-effect relationship. This paper explores the way of expressing causality in argumentative writing in Croatian as a mother tongue (L1), and a foreign language (L2). The study investigates Croatian L1 and L2 speakers’ use of causative connectives in various types of syntactic structures, based on the corpus of 110 argumentative essays (Croatian L1 N=55, Croatian L2 N=55). The results show that in order to express causality, L1 and L2 speakers use the same connectives, in the same syntactic types, but not at the same frequency. Croatian L1 speakers showed strong preference for using pa as a typical causal connective for coordinated and jer for subordinate compound sentences. In comparison to Croatian L1 speakers, L2 speakers showed two tendencies: to overuse some connectives (jer, zato što), and to underuse the others (pa).