Dreaming, by Gerald Laing, disappeared on Sunday afternoon. It was last seen by museum staff at 15:45.
Strathclyde Police have started to examine CCTV images from a number of areas within the museum.
Management said it was the first time a piece had been stolen since the building reopened in 2006 after a major refurbishment.
A spokesman for Glasgow Life, which manages the city museums, said: "This was a deliberate act.
"Someone has stolen from the people of Glasgow. As with all of our collections, this work belongs to them.
"We are working with the police and other agencies and would appeal for the safe return of this work of art."
He said there had been more than nine million visitors to Kelvingrove since it reopened, with no previous incidents of work being taken from public view.
"Thanks to the quick action of staff, we have been able to identify a short timeframe where we believe the bronze was stolen and are in the process of examining CCTV footage from across the museum to identify those responsible," he added.
Artist Laing was born in Newcastle-upon-Tyne and lived on the Black Isle, near Inverness.
He died, aged 75, in November last year.
Laing spent much of the 1960s working in pop art in New York and was a close friend of artists Andy Warhol and Roy Lichtenstein.
His most famous works included images of actresses Brigitte Bardot and Anna Karina.
A bronze sculpture worth £20,000 has been stolen from Kelvingrove Museum in Glasgow.