Authors of written texts may mark the use of verbal irony in a variety of ways. One possibility for doing so is the use of so-called co-textual markers of irony (i.e., support strategies that open up a non-serious frame). This study aims to classify and categorize these co-textual irony markers. A content analysis of 2,042 co-textual utterances of irony across four text genres (advertisements, newspaper columns, book and film reviews, and letters to the editor) shows that three categories of support strategies could be identified: other ironic utterances, tropes and mood markers. The use of irony support strategies was positively related to the genre of newspaper columns: columns used more ironic utterances and tropes as irony support strategies than the other genres in the corpus.