Bärtschi has played with the Swiss national junior team on four occasions. He played in the Under-18 world championship in 2009 and 2010, scoring a goal and two assists in both tournaments for Swiss teams that finished in 8th and 5th place respectively. He then appeared with the under-20 team at the 2011 World Junior Ice Hockey Championships, scoring a goal and an assist in another fifth-place finish. He returned for the 2012 tournament, but appeared in only two games before suffering a concussion that forced him out of the event.