The unnamed oil-on-canvas painting of five women and a girl is signed "Vincent" in one corner, The (London) Telegraph reported Thursday.
Mimara Museum spokesman Darko Glavan said Dutch art expert John Sillevis confirmed the painting was a work by Van Gogh and probably painted in 1882. Glavan told The Telegraph the museum was performing more tests before making an official announcement.
The museum was established to display the collection of Croatian art lover Ivan Topic Mimara, who died in 1987. Of the 3,000-item collection, the museum has cataloged about 1,000 pieces.