Klaasen played Jamie Caven in the first round of the 2014 World Championship and lost 3–1 as he hit just 17% of his darts at doubles. At the German Darts Championship he reached the semi-finals of a European Tour event for the first time by defeating Michael van Gerwen 6–5 in the quarters. He played Justin Pipe and was denied a place in the final as Pipe took out a 134 finish in the deciding leg. Klaasen was narrowly beaten 9–8 by Andy Hamilton in the third round of the UK Open. At the European Championship, Klaasen knocked out reigning champion Adrian Lewis 6–4 in the first round and Caven 10–7 to reach the quarter-finals for the second year in a row, where he lost 10–5 to Mervyn King. Klaasen averaged 108.74 in beating James Wade 6–4 in the first round of the Players Championship Finals, but then averaged nearly 20 points lower as he missed 22 doubles in the next round against Dean Winstanley to be beaten 10–5.