He first appeared in Series 39 at 14 years old, where he lost to Mike Jones on a crucial conundrum. He returned 10 years later after passing another audition, and reeled off 8 impressive wins, including 100 on his debut. After setting the highest score of the series (later surpassed by Charlie Reams) he scored under 100 in his final three games, but still became #1 seed with a points total of 790. This points total was also surpassed by Reams, who scored 820 and Martin Bishop who scored 809.
In the quarter-final, Mubeen gave one of the performances of the series, scoring 124 out of a possible 127 including the nine letter word NOTARISED. Mubeen scored all maximums at the numbers and conundrum and dropped just three points on the letters. Charlie Reams beat Kai Laddiman in the first semi-final, leaving Mubeen to face Martin Bishop in the second one. Mubeen took the lead with SPATIAL and ROMAINE but Bishop got back into the game when Mubeen had PRECASTED disallowed (the past participle of PRECAST is PRECAST). However, when Bishop had SOMAINE disallowed in the final letters game, Mubeen was beyond reach and topped off a good performance by taking the points from the final numbers and conundrum.
In the final #1 seed faced #3 seed, and the game was very close, first of all Reams missed STEMMED in the first round, but Mubeen had SLOPERS x disallowed in the next round. The players scored in the next two rounds, before Mubeen decided to pick six small numbers. Reams declared nothing while Mubeen declared 929 but had miscounted and got no points. In the second "half", Junaid took the lead with ORGANDIE and extended it when Reams had ALIENER disallowed. Mubeen held onto this lead until the final numbers, where Reams made a tactical choice of 4 large, but it didn't work because both players got the target and put their pens down after 20 seconds. Mubeen had a 14 point lead going into the conundrum, but it was Reams that solved ERACLOSES (CASSEROLE) and lost the final by just 4 points, 88 – 84. Mubeen returned for Championship of Champions XIII, taking out Tony Warren before encountering Charlie Reams again in the quarter final. This time he was not so lucky and lost on a crucial conundrum, 88 – 79.
In 2010, he returned to the studio for a deciding match against Charlie Reams. After a brilliant start by Reams, Mubeen pulled into the game thanks to the altered large numbers games, meaning that as they went into the conundrum, Reams' lead was down to 10 points, but Reams took the glory after unravelling KILLABAAA in half a second.
Outside of Countdown, he also appeared on the show Brainteaser (on the same episode as another Coundown player Joseph Bolas).
Mubeen was the first 15-round series champion to have previously appeared on the show before the series that he won (another, Kirk Bevins, would appear in the following series). He was also the first one to have ever been beaten before winning his series, although this occurred during the 9-round era.
|#||Date||Type||Contestant 1||Score||Contestant 2||Guest||Lex||Max|
|2342||4/09/1998||P||Mike Jones||51 – 40||Junaid Mubeen||Barry Cryer||Anna Hall||70|
|4673||22/09/2008||P||Julie Rees||42 – 100||Junaid Mubeen||Andrew Sachs||Susie Dent||144|
|4674||23/09/2008||P||Junaid Mubeen||92 – 79||Hazel Jones||Andrew Sachs||Susie Dent||129|
|4675||24/09/2008||P||Junaid Mubeen||121 – 67||David Williams||Keith Barron||Susie Dent||134|
|4676||25/09/2008||P||Junaid Mubeen||106 – 49||Darren Stibbs||Keith Barron||Susie Dent||117|
|4677||26/09/2008||P||Junaid Mubeen||106 – 72||Tony McCreadie||Keith Barron||Susie Dent||139|
|4678||29/09/2008||P||Junaid Mubeen||94 – 45||Gerard Doyle||Keith Barron||Susie Dent||122|
|4679||30/09/2008||P||Junaid Mubeen||74 – 62||Jonathan Gilligan||Barry Cryer||Susie Dent||117|
|4680||1/10/2008||P||Junaid Mubeen||97 – 27||Margaret Batters||Barry Cryer||Susie Dent||122|
|4728||8/12/2008||QF||Neil MacKenzie||57 – 124||Junaid Mubeen||Jo Brand||Susie Dent||127|
|4731||11/12/2008||SF||Junaid Mubeen||96 – 56||Martin Bishop||Jo Brand||Susie Dent||115|
|4732||12/12/2008||GF||Junaid Mubeen||88 – 84||Charlie Reams||Gyles Brandreth||Susie Dent||118|
|4734||13/01/2009||CP||Junaid Mubeen||80 – 55||Tony Warren||Andrew Sachs||Susie Dent||116|
|4742||23/01/2009||CQF||Junaid Mubeen||79 – 88||Charlie Reams||Alastair Stewart||Susie Dent||128|
|S29||16/08/2010||S||Charlie Reams||87 – 67||Junaid Mubeen||Gary Osborne||Susie Dent||117|