<jats:title>Abstract</jats:title><jats:p>This paper describes the structure determinations of two new ichthyotoxic bis‐quinolizidine alkaloids from the marine sponge <jats:italic>Petrosia seriata</jats:italic>. The structural elucidations are mostly based on homonuclear 2D‐<jats:sup>1</jats:sup>H NMR experiments.