The women, eight singers and one dancer, told the Associated Press they were sexually harassed by the 78-year-old during encounters taking place over 30 years, starting in the 1980s.
Domingo, considered one of the best opera singers of all time, allegedly put his hands up the skirts of one woman and kissed others on the mouth without their consent.
"A business lunch is not strange. Somebody trying to hold your hand during a business lunch is strange, or putting their hand on your knee is a little strange," one of the accusers said. "He was always touching you in some way, and always kissing you."
The women say their careers were affected negatively by Domingo's inappropriate behaviour, and they eventually all had to try to evade the famous singer, who has had more than 4,000 performances worldwide.
One singer, who was 27 at the time, said she felt panicked and trapped.
"I was totally intimidated and felt like saying no to him would be saying no to God. How do you say no to God?" she said after Domingo tried to pursue her by calling her repeatedly.
Eventually, she reluctantly agreed, saying: "I wasn't going to have an opera career if I didn't give in."
"He picked me up in his BMW and I got in the car with him. He was very excited. He was touching my knee," she said, adding that they drove to his apartment near the opera's Dorothy Chandler Pavilion, where champagne was waiting.
"We were sitting on the couch and at some point, he started kissing me," she said.
The woman said he then led her to a bedroom where he took her clothes off, then undressed himself. They engaged in "heavy petting" and "groping", she said.
One of the women said she had sex with him twice, including at the Biltmore hotel in Los Angeles.
When Domingo left for a performance, the woman said he put $10 on the dresser, saying, "I don't want you to feel like a prostitute, but I also don't want you to have to pay to park".
More about: Placido-Domingo