Edith Wharton's geographical boundary crossings - as travel writer, cosmopolitan, transatlantic figure, American in Paris - have been extensively documented. Equally her literary motif of "thresholds", with its dangers for protagonists crossing "beyond", has been the subject of much scholarly debate. Still little discussed, however, are the author's imaginative border crossings in terms of genre - the focus of this paper. Wharton's remarkable career spanned poetry, plays, novels, novellas, short stories, architecture and design manuals, critical writings, journalism, memoirs, travel writing and cultural history. Yet in the "dazzling resurrection" (Cynthia Griffin Wolff) of Wharton's reputation over the past forty years, recognition of the writer's extraordinary range and dexterity of genre and its impact on her career has remained muted. This paper outlines three aspects of Wharton's genre crossings. First, it considers ways in which the author - still best known as novelist and short story writer - employed genres with which she is least associated, particularly poetry and playwriting, to present - at times to camouflage - some of her most daring and subversive work. Secondly, the paper outlines examples of Wharton's genre fusions or slippages - work that cannot be easily categorized by a single genre. These genre crossings, I suggest, illuminate a more modern writer through a design that has still to be considered in recent discussions of Wharton's engagement with modernism. And finally, I suggest her work in the field of critical writings in which she crossed American and European literary traditions opened up a new approach to the genre. I conclude that considerations of the writer in relation to genre and her manoeuvring of genre are essential to the ongoing process of reshaping understanding of Wharton's career.