Helena Carr, 77, was declared to be dead after losing consciousness as a result of a brain aneurism in the Austrian city of Vienna on Thursday night.
"Her little heart continues to beat but her brain has haemorrhaged with a massive amount of blood," Mr Carr said in a statement on Saturday.
"She was the light of my life, the little friend always there.
"No one ever smiled more, or with more spirit."
As the longest serving premier in NSW history, Mr Carr led the NSW Labor Party to three consecutive electoral victories and prepared the state for the Sydney 2000 Olympics.
He said it would have been "inconceivable" to have won office and held the premiership for more than a decade "without the steadiness of her companionship, her sense of fun and her lambent eyes".
Bob Carr says his wife Helena "was the light of my life, the little friend always there".
"On Thursday we walked in autumn weather through Vienna, had lunch with two Australian friends, walked some more and went to the opera," he said.
"She was full of zest and jokes as we walked back to our hotel.
"Within 20 minutes she referred to strange back pain, then a headache and nausea.
"Our 50-year partnership ended in the hotel bathroom when she sunk into my arms and I broke her fall to the floor.
"Her eyes closed for the last time while I begged her not to leave me."
Ms Carr was born in Malaysia and came to Australia to study economics at the University of Sydney.
The pair met in Tahiti in early 1971 when Mr Carr was on a stopover on a trip back from the United States.
The former premier described his wife as an accomplished businesswoman who became an expert in security printing.
"The light has gone out of my life," he said.
"I know many have faced this challenge, the loss of a life partner, the journey no one wishes.
"One reason to (keep) trying is my sense she is there telling me to go on - for her."
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