The formerly monotypic genus Carexomyza Roháček, 2009 (Diptera: Anthomyzidae) is revised to include one Palaearctic, viz. C. caricis (Roháček, 1999), and three new Nearctic species, viz. C. lonsdalei sp.n., C. marshalli sp.n. and C. browni sp.n., all from Canada and the northern United States of America. Carexomyza is re-diagnosed and its phylogenetic position within extant Anthomyzinae discussed. All species are described or diagnosed and illustrated and a hypothesis about their relationships (based both on morphological and molecular data) is presented. The biology of Carexomyza species is treated for the first time, with new information about habitat, host-plant association, life history and adult behaviour. The distribution of Carexomyza species is summarized.