In the 2012 FIM Junior World Championship, Vlaanderen bettered the previous season's result, riding to seventh overall.

Vlaanderen then followed this up by finishing runner-up in that year's Junior World Championship, winning the second race en route to this.

On top of this, Vlaanderen competed in his first two MX2 grand prix in the 2014 FIM Motocross World Championship, with a best finish of thirteenth in race one in the Czech Republic.

His performance throughout the season, would earn Vlaanderen his first call up to compete for The Netherlands at the 2018 Motocross des Nations.

[9] As a team, the Dutch were able to finish second overall after his teammates Jeffrey Herlings and Glenn Coldenhoff won all three races.

He missed several rounds of the season and finished eighth in the final standings, picking up a race win and four overall podiums on the way.

For the 2020 FIM Motocross World Championship, Vlaanderen had to move up to the MXGP class and was picked up by the Gebben Van Venrooy Yamaha team.

After a start to the season where he steadily improved, Vlaanderen was able to record a dominant double race victory and grand prix overall win in Sardinia.

He picked up a single race win at the Czech round and made his fourth appearance at the Motocross des Nations, where the Dutch team was hampered by the injury of Glenn Coldenhoff.