Dortmund is the second destination available from Sibiu, after the route London Luton became operational on June 14.
Wizz Air currently operates 88 routes from Romania to 15 countries and carried 3.2 million passengers to and from Romania last year, compared to 2.7 million in 2012.
The Hungarian airline operator has flights from five airports in Romania and will start operations on a sixth, Craiova, this summer.