Dekker was the sixth seed for the 2012 BDO World Darts Championship, where he lost 2–3 in the first round against compatriot and eventual champion Christian Kist despite averaging over 96. The following year, Dekker was seeded seventh and this time reached the quarter-finals, surviving a match dart in the first round against Jeffrey de Graaf, then edging Thompson once more in the second round this time 4–3 having trailed 3–2. In the quarters, Dekker led Richie George 3–1 but eventually lost 5–4.