Junk made his MMA debut against UFC veteran and former UFC heavyweight champion Ricco Rodriguez and he was submitted by a front choke applied by Rodriguez. His next notable fight was his UFC debut against Christian Wellisch, which he lost by heelhook submission. He drew his last official fight at X-1 – New Beginning against Lolohea Mahe on February 27, 2009.
The Ultimate Fighter
In late 2009, Junk attempted to return to the UFC, this time by competing in The Ultimate Fighter: Heavyweights. During team selections, Junk was selected 5th by Quinton "Rampage" Jackson and 10th overall. Junk's first fight was planned (by opposition coach Rashad Evans) to have been against his good friend Justin Wren, but after Justin expressed a desire to not fight his good friend, the match never took place.
Instead, Junk's first fight came in the 7th episode where he lost a majority decision to Matt Mitrione.
During this fight, both men were visibly tired in the second round and Junk even suffered a torn retina and from the first minute of the fight, had one eyelid "inside out." 
This torn retina was later revealed to require laser surgery, leading to fears that Junk's career could be over. This was later proved to be incorrect and that Junk could resume training in a couple of months.
Mixed martial arts record
|Professional record breakdown|
|11||6 wins||2 losses|
|Draw||6–2–1||22px Lolohea Mahe||Draw||X-1 – New Beginning||February 27, 2009||3||5:00||Hawaii, United States|
|Loss||6–2||Christian Wellisch||Submission (Heel Hook)||UFC 76: Knockout||September 22, 2007||1||3:19||California, United States||UFC Debut|
|Win||6–1||Jimmy Ambriz||TKO (Corner Stoppage)||MFC 12: High Stakes||June 22, 2007||1||5:00||Alberta, Canada|
|Win||5–1||Dominic Richard||Submission (Verbal)||MFC: Unplugged 3||April 20, 2007||1||Alberta, Canada|
|Win||4–1||John George||KO (Punch)||ICON Sport: All In||February 9, 2007||1||0:10||Hawaii, United States|
|Win||3–1||Corey Salter||Decision||Extreme Wars 5: Battlegrounds||October 6, 2006||3||3:00||Hawaii, United States|
|Win||2–1||Hideki Tadao||TKO (Strikes)||Rumble on the Rock 9||April 21, 2006||1||2:20||Hawaii, United States|
|Win||1–1||Vilatonu Fonokalafi||TKO (Strikes)||Rumble on the Rock 8||January 20, 2006||1||3:32||Hawaii, United States|
|Loss||0–1||Ricco Rodriguez||Submission (Front Choke)||Rumble On The Rock 7||May 7, 2005||2||0:42||Hawaii, United States|
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