He is a member of Dalibor Kupka's training group at ASC Dukla Praha.

In the 400 metres, he advanced from heats by setting a new national record and personal best of 44.91 but did not manage to repeat the feat in semi-finals and finished fifth in his run.

In his last race of the 2012 season, Maslák set a national record of 20.59 in 200 metres dash.

At 2013 European Indoor Championships in Gothenburg, Pavel Maslák won a gold medal in 400 metres distance.

As a part of the Czech 4 x 400 metres relay team, he added a bronze medal.