The United Rugby Championship encounter was due to take place at Rodney Parade on Saturday, but numerous positive Covid-19 cases have been found within both squads.
Cardiff have liaised with the Dragons, the URC Medical Advisory Group and Public Health Wales throughout and it has been deemed that the fixture can no longer take place as scheduled.
The United Rugby Championship will now consider available dates to reschedule the game.
It is the second consecutive Cardiff fixture postponed due to Covid-19, with case rates soaring across the country.
Extra testing has been taking place and the club will continue to work with all governing bodies, while following enhanced protocols and all government guidelines.
