The aim of this study was to assess the usefulness of oregano (Origanum vulgare L.) and thyme (Thymus vulgaris L.) extracts to decrease mycotoxin contents and improve the hygienic quality of maize (Zea mays L.) silage. Under laboratory conditions, maize silage samples were fermented with oregano (OE), thyme (TE), oregano and thyme mixture (MIX), and two commercial inoculants. After 90 days of fermentation, silos were opened and silage samples were taken for evaluation of mycotoxin concentrations and for hygienic quality analysis: assessment of fermentation parameters, the content of biogenic amines, and microbiological status. It was determined that the mycotoxin concentrations decreased differentially: ochratoxin A concentration was below the detection limit after treatment with the TE and MIX extracts, the lowest zearalenone and deoxynivalenol concentrations were achieved with the OE extract treatment, T-2 toxin concentration was significantly lower after treatment with the TE extract, and HT-2 toxin concentration was lower after treatment with the MIX extract. The lowest content of biogenic amines in maize silage was established with the MIX extract. Concerning the silage hygienic quality, the best results of fermentation parameters and microbiological status were also achieved with the MIX extract. The present study indicated that oregano and thyme herbal plant extracts can be used to decrease mycotoxin concentrations and improve the hygienic quality of maize silage.