Zambian light-middleweight Michael Norgrove, who was based in London, collapsed on March 31.
The 31-year-old was treated for bleeding on the brain following the bout against Sedgley’s Tom Bowen at The Ring in Blackfriars, south London.
BBBC General secretary Robert Smith said: “We were informed of his death this morning. The whole sport feels for his family and we need to let it sink in.
“He was a nice little boxer – but forget boxing for now, it’s very sad news indeed.”
Michael Norgrove had been taking part in his first fight after a two-year break from the sport.
The boxer was undefeated and had he beaten Tom Bowen it would have been a sixth straight win.
Michael Norgrove was a sparring partner of boxer James DeGale, who won a gold medal in the Beijing Olympic Games.
On Saturday morning James DeGale Tweeted: “So sad to hear about the passing of Michael Norgrove. He will be sadly missed.”
Michael Norgrove had trained at the Repton Club in east London.
A statement on the club’s website said it was “saddened” by the news that the boxer had collapsed “doing what he loved”.
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