Drepanolejeunea laciniata Qiong He et R.L. Zhu sp. nov., is described and illustrated from Doi Inthanon National Park, Chom Thong District, Chiang Mai Province, northern Thailand. It is similar to Drepanolejeunea pulla (Mitt.) Grolle and D. erecta (Steph.) Grolle, but differs mainly in its large leaf lobule that is 1/2-2/3 as long as the leaf lobe, the free lateral lobular margin proximal to the notch bordered by 9-13 rectangular cells, the obovate perianth with dense apical laciniae, and usual presence of median ocelli in the leaf lobe.