[1] 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.
[1] In 2014, Dekker was seeded sixth and faced a fellow Dutch player in the first round for the third year in a row, this time defeating Benito van de Pas 3–0.
He then beat Geert De Vos 4–2 and followed this with his first ever professional victory over three-time world champion Martin Adams, winning 5–2.
[7] Dekker reached the third round of the European Darts Open by defeating John Henderson 6–4 and Dave Chisnall 6–3, but was thrashed 6–0 by Gary Anderson.
[8] Dekker made his debut in the Players Championship Finals after being placed 54th on the Order of Merit and beat Steve West 6–3 in the first round, before losing 6–1 to Justin Pipe.
At the end of the year, he dropped to 56th place in PDC Order of Merit after not being able to defend his prize money from 2017 Players Championship Finals.
Dekker made it for the third time in a row to the second round of the World Championship, after winning over Ryan Joyce and losing to Jonny Clayton.
It was his only major in 2020 season and because Dekker was not able to qualify for another World Championship, he dropped out of top 64 of PDC Order of Merit, losing his Tour card after 4 years.
He was automatically qualified for the Final stage, but gaining just two points in the Q-school Order of Merit, he finished 44th in the rankings and did not get a new Tour card.