The 63-year-old wrestler said he was "grateful" to have known the late WWE star, who passed away from kidney failure shortly after entering hospice care.
In a touching message on Twitter, Hulk wrote: "George 'the Animal' Steel, RIP my brother, only love, only grateful. HH"
One of the WWE's most notorious villains, George, whose real name was William James Myers, was known for his green tongue, hairy torso and unpredictable style.
He was diagnosed with Crohn's in 1988, an inflammatory bowel disease which has no cure but can be brought into remission, and had his colon removed in 2002.
His wife Patricia told gossip website TMZ.com he died yesterday of kidney failure, while pro-wrestling agent Eric Simms revealed on Facebook that George had only just entered hospice care.
Other members of the wrestling community also shared their condolences on social media.
George's biggest rivalry in the ring was WWE Champion Bruno Sammartino and, although he never won an official WWE Championship, he was inducted into the WWE Hall of Fame in 1995.
He was a vocal advocate against Crohn's and wrote about his struggles in his autobiography, 'Animal'.
The late wrestler also appeared in Tim Buton's film 'Ed Wood' in 1994 and featured in the video game 'WWE SmackDown! Here Comes the Pain' as a legend character.
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