Despite leaving her judging role on the ITV show in December, Mrs O showed she's still in touch with past contestants by tweeting Nicholas to praise his new song 'Answerphone'.
Sharon wrote: "I'm so proud of you! #Answerphone is fabulous!"
Nicholas finished runner-up to Sam Bailey on the tenth season of X Factor, which wrapped in December 2013. He signed a record deal with Sony's RCA label the following month.
Sharon, meanwhile, was Sam's mentor so she stepped away from the show as the winning judge.
As well as sending her support to Nicholas, Sharon has also been vocal in praising Sam, who released her debut album The Power of Love in March.
Just before the album hit the top spot in the chart and became the fastest-selling one of the year, a proud Sharon had tweeted: "I'm counting down the hours till it's official & your album is number 1. Remember, you've always been my number 1. So proud."
Sharon has also agreed to be godmother to pregnant Sam's third child.
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Watch Nicholas' music video for 'Answerphone' below: