AbstractManipulation of the fermentation of the marine‐derived fungus Penicillium chrysogenum by addition of CaBr2 resulted in induced production of bromodiphenyl ether analogs. Two new free‐radical‐scavenging polybrominated diphenyl ethers, 1 and 2, and three known diphenyl ethers, 3,3′‐dihydroxy‐5,5′‐dimethyldiphenyl ether (3), and an inseparable mixture of violacerol‐I (4) and violacerol‐II (5) were isolated. The structures of the two new polybromodiphenyl ethers 1 and 2 were assigned by combined spectroscopic‐data analysis, including deuterium‐induced isotope effect. Compounds 1–3, and a mixture of 4 and 5 exhibited radical‐scavenging activities against 1,1‐diphenyl‐2‐picrylhydrazyl with IC50 values of 18, 15, 42, and 6 μM, respectively. With the exception of 3, the compounds were, therefore, more active than the positive control, ascorbic acid (IC50 20 μM).