The 'American Idol' judge showed the ultimate declaration of his love for the actress on US TV's 'The Jimmy Kimmel Show' where he unveiled his new inking during a performance to promote his latest album 'Fuse'.
Keith made sure no-one missed the romantic gesture by wearing a short sleeved top while he crooned away on his guitar.
The 45-year-old star already had the name of the actress etched onto his right arm in script font, but now sports a re-worked version of the tattoo featuring an additional Celtic design around the original inking.
The couple - who have been married for seven years - have two daughters together, five-year-old Sunday and three-year-old Faith. Nicole also has two adopted children, 18-year-old, Connor and 20-year-old Isobella, with her ex-husband Tom Cruise.
Nicole has previously said she'd love for one of her daughters to follow in Keith's footsteps and become a singer.
She said: ''[Sunday] has really good pitch. I'd love it if she sings. The great thing about being married to a musician is you have music in the house all the time. [Keith will] play the piano at 7 a.m. ... We have breakfast around the piano.''
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