A revision of the genus Lejeunea in Malaysia based on examination of about six hundred fresh collections and about four hundred herbarium specimens leads to the recognition of 30 species and 2 varieties. All species are keyed and illustrated, their morphological characters are described and discussed in detail, and distribution and habitat in Malaysia and world distribution are given. In addition, notes are presented on little-used or neglected morphological characters including superior central cells, oil bodies and vegetative propagules. Two species, Taxilejeunea cuculliflora Steph. [= L. umbilicata (Nees) Nees] and Eulejeunea infestans Steph. (=L. papilionacea Steph.) are new synonyms. Eight species are reported for the first time from Peninsular Malaysia [L. alata Gottsche, L. cocoes Mitt., L. dimorpha Kodama, L. fleischeri (Steph.) Mizut., L. micholitzii Mizut., L. papilionacea Steph., L. tuberculosa Steph., and L. umbilicata (Nees) Nees] and one species from East Malaysia, i.e. L. compacta (Steph.) Steph.