Attorney Bobby Samini, who is representing Sterling, told the Los Angeles Times in an email that the allegations are "completely baseless."
In a lawsuit filed in Los Angeles Superior Court and obtained by multiple media outlets, Maiko Maya King alleges that she met Sterling in 2005, when she was married with two children, and was encouraged to leave her husband.
From 2005 to 2011, she was involved with Sterling, who "supported her financially and she worked for him and his foundation," the suit states. Sterling also allegedly asked King about her former husband, an African-American, saying, "How could you be married to a black man?" and "Why would you bring black people into the world?"
The lawsuit alleges that Sterling's views led to his and King's breakup in 2011, but King was told by Sterling in December 2013 that he needed her as a caretaker and personal assistant because "she was the only one who could do this for him."
While discussing her employment, Sterling introduced her to "V," a woman he called his girlfriend.
But contrary to King's arrangement, which the suit states would pay her $10,000 a month, Sterling "dangled money" only if she would have sex with him. She refused, and she was fired on May 7, the suit states.
Sterling made headlines over the weekend after attending a predominantly black church service in South Los Angeles.
Sterling told KNBC-TV he went to Praises of Zion Missionary Baptist Church on Sunday to support the church and said the service was "beautiful."
The station said the church's pastor met Sterling recently and invited him to worship with the congregation. Sterling received a warm welcome, and Pastor J. Benjamin Hardwick told him the congregation was praying for him.
Sterling has filed a lawsuit against the NBA asking for damages in excess of $1 billion.
Sources told ESPN.com's Ramona Shelburne he was found by experts to be mentally incapacitated, paving the way for Shelly Sterling to become the sole trustee of the family trust and empowering her to sell the team to former Microsoft chief executive Steve Ballmer. That deal awaits final approval by the NBA's Board of Governors.
Information from The Associated Press was used in this report.