A new species, Carex borealifujianica Y.F. Lu & X.F. Jin (Cyperaceae, sect. Occlusae of core Carex clade) is described and illustrated from northern Fujian, China. In addition to morphological comparisons with its relatives, comparative micromorphology of utricles and achenes of seven species in Carex sect. Occlusae was examined. Micromorphology of utricles and achenes revealed the similarity of Carex borealifujianica and C. ligulata. Morphologically, this new species is similar to Carex ligulata in having lateral spikes remote and densely flowered, as well as utricles densely hispidulous, but differs in having 2 or 3 narrowly clavate staminate spikes, leaves 2.5–5 mm wide with sheaths sparsely pilose, and achenes emarginate at the apex. The phylogenetic analysis from two nuclear DNA regions (ETS and ITS) and two chloroplast DNA regions (matK and trnL-F) of 68 taxa resolved C. borealifujianica as a distinct species.