The behaviour of Myrothecium roridum, artificially inoculated on cultivated rocket (Eruca sativa), has been evaluated under eight different temperature and CO₂ concentration combinations (from 14-18 °C to 26-30 °C and with 400-450 or 800-850 ppm of CO₂). The pathogen isolate used for this study was inoculated on rocket and disease severity increased with high temperatures for both CO₂ levels. Verrucarin A and roridin E mycotoxins were produced under all the tested temperatures at high CO₂ conditions. The maximum level of verrucarin A was found at 14-18 °C and 800-850 ppm of CO₂, and the maximum roridin E production was detected at 26-30 °C with 800-850 ppm of CO₂. The results obtained in this study show that both the CO₂ concentration and the temperature influence disease severity and mycotoxin production in different ways. An increase in temperature, which is favourable for attacks of the pathogen, could induce the spread of M. roridum in temperate regions, and this pathogen could take on even greater importance in the future, considering its ability to produce mycotoxins.