The easiest way to get to Viirus is by tram number 9, which has a stop right outside the door. Tram number 8 has it's endstop at the end of the street Välimerenkatu, while tram number 7 and 6T have stops at the start of street next to Hotel Clarion. Both stops are only a few minutes walk away from the theatre.
The closest stop with the metro is Ruoholahti, an 8 minute walk from the theatre.