<jats:title>Abstract</jats:title><jats:p>Two new, <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold>, along with one known isoindolone, <jats:bold>3</jats:bold>, were isolated from the AcOEt extract of <jats:italic>Lasiosphaera fenzlii</jats:italic> <jats:sc>Reich</jats:sc>. The structures of these compounds were determined as 4,6‐dihydroxy‐1<jats:italic>H</jats:italic>‐isoindole‐1,3(2<jats:italic>H</jats:italic>)‐dione (<jats:bold>1</jats:bold>), 4,6‐dihydroxy‐2,3‐dihydro‐1<jats:italic>H</jats:italic>‐isoindol‐1‐one (<jats:bold>2</jats:bold>), and clitocybin A (<jats:bold>3</jats:bold>) on the basis of chemical and spectroscopic evidences. The bioactivity assays revealed that all of them were devoid of significant cytotoxicities against tumor cells, whereas <jats:bold>1</jats:bold> exhibited potent antiangiogenic activity by inhibiting the secretion of vascular endothelial growth factor (VEGF) in A549 cells.