<jats:p>Six new compounds including two furanone derivatives sclerotiorumins A and B (<jats:bold>1</jats:bold> and <jats:bold>2</jats:bold>), one novel oxadiazin derivative sclerotiorumin C (<jats:bold>3</jats:bold>), one pyrrole derivative 1‐(4‐benzyl‐1<jats:italic>H</jats:italic>‐pyrrol‐3‐yl)ethanone (<jats:bold>4</jats:bold>), and two complexes of neoaspergillic acid aluminiumneohydroxyaspergillin (<jats:bold>5</jats:bold>) and ferrineohydroxyaspergillin (<jats:bold>6</jats:bold>) were isolated from the co‐culture of marine‐derived fungi <jats:italic>Aspergillus sclerotiorum</jats:italic> and <jats:italic>Penicillium citrinum</jats:italic>. Compound <jats:bold>3</jats:bold> was the first natural 1,2,4‐oxadiazin‐6‐one. Compound <jats:bold>5</jats:bold> showed significant and selective cytotoxicity against human histiocytic lymphoma U937 cell line (<jats:italic><jats:styled-content style="fixed-case">IC</jats:styled-content></jats:italic><jats:sub>50</jats:sub> = 4.2 μ<jats:sc>m</jats:sc>) and strong toxicity towards brine shrimp (<jats:italic><jats:styled-content style="fixed-case">LC</jats:styled-content></jats:italic><jats:sub>50</jats:sub> = 6.1 μ<jats:sc>m</jats:sc>), and oppositely increased the growth and biofilm formation of <jats:italic>Staphylococcus aureus</jats:italic>.