Ahead of the final performance, Osbourne said his emotions were "all over the place".
Rehearsing for the big finale, he told the BBC: "Since I've got to this building, I've been happy, I've been tearful. Let's see what happens."
Sabbath began as a blues band, before morphing into its own genre. In their early years, Sabbath's slow-building anthems and hints of Satanism in song lyrics earned them ridicule from mainstream critics but stirred an underground fan base.
Credited with creating the heavy metal genre in the depths of 60s industrial Birmingham, the band went on to release 19 studio albums and 31 singles.
"One of the proudest things I have in my heart is the fact that Black Sabbath wasn't a band that was created by some big mogul," Osbourne said.
"It was four guys who said, 'Let's have a dream,' and it came true beyond our wildest expectations."
Osbourne's fame underwent a surprising shift when he began starring in the 2002 MTV reality TV show The Osbournes, which portrayed him as a lovable, murmuring goofball and family man.
He described his life with the band as "the most incredible adventure", but conceded that Sabbath had "run its course".
Fans need not be completely disheartened by the end of Black Sabbath, however, because Osbourne will continue to perform as a solo artist.