The Cinnamomum species (Lauraceae) have been used in folk medicine for its sweating, antipyretic, and analgesic effects. There are only two papers describing the constituents of leaves of Cinnamomum reticulatum Hayata. In the course of screening for biologically and chemically novel agents from Formosan Lauraceous plants, C. reticulatum was chosen for further phytochemical investigation. A new butanolide, isoreticulide ((4R,3E)-4-hydroxy-5-methylene-3-octadecylidenedihydrofuran-2-one) (1), along with nine compounds including one sesquiterpenoid, (3-methoxy-5H-9,11-dioxabenzo[3,4]cyclohepta[1,2-f])inden-7-yl)-methanol (2); six benzenoids, p-hydroxybenzoic acid (3), p-hydroxybenzaldehyde (4), protocatechuic acid (5), ferulic acid (6), trans-methyl p-coumarate (7), and p-dihydrocoumaric acid (8); and two amides, N-trans-feruloyltyramine (9) and dihydroferuloyltyramine (10), were isolated from the leaves of C. reticulatum Hayata. These compounds were characterized and identified by comparison of their physical and spectral data (UV, IR, NMR, and MS) with values obtained in the literature. In addition to 3 and 4, all of these compounds were found for the first time from this plant. In this paper, we report the isolation and structural elucidation of butanolide 1 and sesquiterpenoid 2.