PmTFL1, Prunus mume ortholog of TFL1 (TERMINAL FLOWER 1), was isolated and characterized to investigate the relationship to floral bud formation in Japanese apricot (P. mume). PmTFL1 consists of a 1251-bp open reading frame (ORF), which encodes 172 amino acid residues, consisting of three introns and four exons. The PmTFL1 sequence shows high identity to Arabidopsis thaliana TFL1 and TFL1 orthologs of other plant species. The transgenic Arabidopsis expressing PmTFL1 under the control of cauliflower mosaic virus 35S promoter produced many rosette leaves and significantly delayed the flowering time. Some of the transgenic plants with higher expression of PmTFL1 took more than 70 days to flowering, showing that PmTFL1 has the same function as the Arabidopsis TFL1 to maintain the vegetative growth and suppress flowering. PmTFL1 transcripts were detected only in leaf buds and young expanding leaves in adult trees and in the leaves, stems, and roots in juvenile seedlings. PmTFL1 was suggested to be involved in the development of juvenile and young vegetative organs.