The news comes after a report, originally published by The Washington Post, and later by USA Today, claimed Wahlberg earned USD 1.5 million, while Williams made less than USD 1,000.
Offering his support to combat harassment and pay inequities in Hollywood, the 46-year-old actor issued a statement saying, "Over the last few days my reshoot fee for 'All the Money in the World' has become an important topic of conversation.
WME donated additional USD 500,000 as well.
"In recognition of the pay discrepancy on the 'All the Money in the World' reshoots, WME is donating an additional USD 500,000 to the Time's Up Legal Defense Fund in Michelle Williams' name, following our USD 1 million pledge to the organisation earlier this month.
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"It's crucial that this conversation continues within our community and we are committed to being part of the solution," they said.
"Today isn't about me. My fellow actresses stood by me and stood up for me, my activist friends taught me to use my voice, and the most powerful men in charge, they listened and they acted. If we truly envision an equal world, it takes equal effort and sacrifice.
"Today is one of the most indelible days of my life because of Mark Wahlberg, WME and a community of women and men who share in this accomplishment. Anthony Rapp, for all the shoulders you stood on, now we stand on yours," she said.
The report about the glaring pay disparity has gone viral on social media and invited criticism by many celebrities, such as Jessica Chastain, Mia Farrow and Judd Apatow.