Biochemistry of bioluminescence of the marine parchment tubewormChaetopterushas been in research focus for over a century; however, the results obtained by various groups contradict each other. Here, we report the isolation and structural elucidation of three compounds fromChaetomorpha linumalgae, which demonstrate bioluminescence activity withChaetopterusluciferase in the presence of Fe2+ions. These compounds are derivatives of polyunsaturated fatty acid peroxides. We have also obtained their structural analogues and demonstrated their activity in the bioluminescence reaction, thus confirming the broad substrate specificity of the luciferase.