James praised the 17-year-old college student and part-time bakery worker on Twitter after watching her sing a rendition of Sam Cooke's soul classic 'A Change Is Gonna Come' at the judges' houses in Antigua.
Last night (6 October), viewers saw a tearful Hannah battle it out in the Girls category and impress judge Nicole Scherzinger and guest judge Mary J Blige to win a place in the live shows.
James, who stormed to victory as last year's X Factor winner with Nicole as his mentor, said: "Hannah has to win this year for me. That is what you call soul! Take note on how to believe in what you're singing from this girl! #xfactor."
James didn't just have praise for Hannah though, as he also said that Tamera Foster was "amazing", adding that the 16-year-old has "star quality".
James, who will release his self-titled debut album next month, went on to have the biggest and fastest selling X Factor single ever with his rendition of 'Impossible', which sold over 1.2million copies.
The 25-year-old rising star is preparing to release his second single 'You're Nobody Til Somebody Loves You', on 20 October and he's also just announced his debut UK and European headline tour!
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Watch Hannah's performance at the judges' houses in the video below:
Check out this year's X Factor Top 12 acts below:
Copyright: ITV Tom Dymond/Thames TV