The 50-year-old actress will be replacing R&B singer Toni Braxton as special guest vocalist in her six-week stint starting from April 1, reported Variety.
The musical launched last year with Fantasia Barrino.
Williams, who starred in Broadway revival of 'The Trip to Bountiful', also has 'Into the Woods,' 'Kiss of the Spider Woman' and 'Sondheim on Sondheim' to her credit.