Diarylheptanoids, (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptane-3-one-5-O-${eta}$-D-xylopyranoside (1, Oregonin), 1,7-bis-(3,4-dihydroxyphenyl)-4-heptene-3-one (2, Hirsutenone), (5S)-7-(3,4-dihydroxyphenyl)-5-hydroxy-1-(4-hydroxyphenyl)-3-heptanone-5-O-${eta}$-D-xylopyranoside (3, Alnuside A), (5S)-1-(3,4-dihydroxyphenyl)-5-hydroxy-7-(4-hydroxyphenyl)-3-heptanone-5-O-${eta}$-D-xylopyranoside (4, Alnuside B), (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptane-3-on-5-O-${eta}$-D-glucopyranoside (5) and 1,7-bis-(4-hydroxyphenyl)-5-hydroxyheptane-3-on-5-O-${eta}$-D-glucopyranoside (6, Platyphylloside) were isolated from the bark of Alnus pendula Matsumura. The structures of these compounds were identified based on the spectral and physicochemical data.