Two new (1 and 3) and two known diarylheptanoids (2 and 4), along with two tetralones (5 and 6), one naphthoquinone (7), four phenylpropanoids (8–11), and one phenol (12) were isolated from the leaves of Juglans mandshurica. Their structures were elucidated on the basis of spectral and chemical data. Compounds 2 and 10 are firstly isolated from this plant and 8 and 12 were isolated from the Juglans genus for the first time. Among these compounds, only 7 exhibited moderate cytotoxicities against cultured MGC-803, A549, K562, and HeLa tumor cell lines with IC50 values of 25.90, 28.60, 39.06, 44.90 μM, respectively.