Ethanolic and aqueous extracts of propolis (0.4 and 0.8%) were used to examine their in vitro impacts on the growth and biogenic amines (BAs) formation by Morganella psychrotolerans DSM 17886 in histidine decarboxylase (HDB) and sardine infusion decarboxylase broth (SIDB). In addition, the extracts effects were monitored in vivo on vacuum packaged sardine fillets with M. psychrotolerans at 3 +/- 1 degrees C for 15 days. Analysis of gas chromatography/mass spectrometry showed that quinolone and flavonoids present in propolis extracts. Aqueous extract of propolis were more effective than ethanolic extract to decrease bacterial load in HDB. The extracts considerably suppressed histamine formation in HDB, although inhibition effect was only found by propolis aqueous extract at doses of 0.4% in SIDB, with 30-fold lower histamine formation. Inhibition effects of propolis extracts on BAs production in fish meat were generally observed apart from noteworthy stimulation effect on histamine production of 0.8% ethanolic propolis extracts.