The Portuguese player, who recently scored his 500th career goal, was photographed holding a Real Madrid jersey with a signed message, which was posted on twitter by the club's official handle.
"To my friend John Abraham, Wish All The Best to you and to Northeast United," said the message.
Co-owner of Northeast United FC John Abraham thanked the Los Blancos star for his support.
He tweeted the photo of Ronaldo and wrote, "Thank you Cristiano!"
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"Arguably the greatest player in the world, @Cristiano is on our side! Lets go #Highlanders! #NEUFC @IndSuperLeague," the club tweeted.
Northeast United FC are at the bottom of the table after losing the first two matches of the season. The Highlanders, in their first home game of the season, will look for inspiration from their fans to beat FC Goa tonight.
On the other hand, fifth-placed FC Goa will look to bounce back after losing at home to Chennai by four goals on Sunday.
Ronaldo, who recently won the European Golden Shoe for a record fourth time, had said at the Golden Shoe award ceremony that he was hungry for more.
He said, "I am not satisfied, I want more. I'm the only one that has four but I want the fifth and the sixth.