Gary Robinson says Jackie Gallagher-Smith, who is married, used him as "an unwitting sperm donor."
He is suing for an unspecified sum, claiming fraud and intentional infliction of emotional distress.
No hearing date has been set for the suit, filed in circuit court this week in West Palm Beach.
A message for Gallagher-Smith's lawyer, Edwin Belz, was not immediately returned.
Earlier, Belz told the South Florida Sun-Sentinel the suit was, "an attempt at extortion."
The suit says Gallagher-Smith, 37, gave birth last month, but Florida law says a child born into a marriage is deemed to be a result of the marriage. A DNA test can't be forced and Robinson has no legal claim to the child, said Cathy Lively, Robinson's lawyer.
"That is why we are seeking damages ... he's not going to be able to ask for a DNA test," Lively said. "He was put into the position of being an unwitting sperm donor."
Robinson said he has been affected professionally. He is out of work as a caddie and is pursuing a career as a professional golfer.
Robinson, 26, began caddying for Gallagher-Smith in February 2004, and soon thereafter began receiving advances from her, he said.
Robinson said he was in an emotional state after ending a long-term relationship, and he passed off some early advances as "innocent playful activity."
The relationship became sexual about two months later and the two would sometimes engage in unprotected sex, he said.
