Overeem was born in Amersfoort, Utrecht[1] and is associated with the Imperial Athletics gym in Boca Raton, Florida where he trains with his younger brother Alistair.
[3] Valentijn was trained at the Chris Dolman gym, where he specialized in kickboxing and sambo before debuting at the Japanese professional wrestling promotion Fighting Network RINGS.
Overeem earned a yellow card for holding the ropes to avoid a takedown at one point, but he made up by outstriking Suren and focusing on kicking his injured leg, finishing the match by knee strikes.
Returning to the fight, Overeem managed to compose himself and take down Babalu by kosoto gake, which the lutador countered by threatening with another armbar from the bottom.
[4] He eventually made his promotional debut against Ray Sefo at Strikeforce: Fedor vs. Silva on 12 February 2011 where he won in the first round by using a neck crank.
[6] On 25 February, Overeem won his fight against Polish kickboxer and mixed martial artist Marcin Różalski at KSW 18 in Płock, Poland.
The fight was held in Miami on the debut event of S-1 Challenge, it ended in a No Contest decision due to an unsafe ring as both fighters fell over the ropes with Wilson falling twice.