Four new dimeric styrenes, <b>1</b>-<b>4</b>, were isolated from an EtOAc crude extract of the seeds of <i>Atalantia monophylla</i>. The biosynthetic pathway of <b>1</b> is proposed to involve a [2 + 2] cycloaddition, while <b>2</b>-<b>4</b> may be generated via a polar mechanism with a carbocation as the key intermediate. The structures of <b>1</b>-<b>4</b> were defined from spectroscopic analysis; experimental and calculated ECD spectra were used to characterize their absolute configurations. When tested against two different cancer cell lines, <b>1</b>-<b>4</b> were not determined to be cytotoxic (IC<sub>50</sub> > 10 μM).