Minnelli, 69, has been in the treatment facility for several days, said The Hollywood Reporter.
Scott Gorenstein, a spokesperson for Minnelli, said she "has valiantly battled substance abuse over the years and whenever she has needed to seek treatment she has done so. She is currently making excellent progress at an undisclosed facility."
The actress, who won the best actress Oscar in 1973 for her role in "Cabaret", has openly spoken about her alcoholism in the past.