People reports that Gordon's rep confirmed that Gordon posted the image to his personal Twitter account, which is now private, on Dec. 22.
The card featured a photo of Gordon and Brown with Santa hats Photoshopped onto their heads, and wrapped presents digitally placed in their laps.
Gordon is currently embroiled in a legal battle with Brown's family over her death.
Brown was found unconscious in a bathtub in her Georgia home in January and spent months in a coma before dying on July 26 in hospice care, at age 22.
Gordon is the target of a $10 million wrongful death lawsuit filed by Brown's conservator, Bedelia Hargrove, on behalf of Brown's family and is also under criminal investigation in relation to her death.
The 25-year-old has denied all allegations that he physically abused his late girlfriend, or that he was responsible for her death, and he has assembled a legal team to defend himself against the accusations.
For more on Gordon's on-going legal troubles, watch the video below.