Snowboarding pioneer Tina Basich alleged that Dave Grohl cheated on her during their relationship, decades before he admitted to fathering a child outside his current marriage.

In her 2003 memoir, “Pretty Good for a Girl: The Autobiography of a Snowboarding Pioneer,” Basich, 55, wrote of the pain of learning that Grohl, also 55, was allegedly having an affair with her and another woman at the same time.

The couple dated for about two years in the late ’90s and broke up around the time Basich broke her leg, sidelining her career for months.

The athlete detailed how “busy” the rocker was with his “million-dollar recording contracts, deadlines with record labels, music videos (and) press tours” — while he “tried to focus on creativity and writing music.”

“The pressure was too much for our relationship,” she admitted. “You can only give up so much of your heart, your career, your time, your mind, and here I was, giving it all up for a man and losing myself in the process.”

Basich felt like she was “taking time away from his career” while putting her own career “on the backseat without even realizing it.”

She wrote: “I don’t know how anyone in their line of work can have a normal relationship with a girlfriend… or two, as it turns out. I found out through the grapevine, when it seemed like everyone in the world knew about it except me.”

Basich admitted she was “so disappointed and angry” with herself “for getting sucked into it.”

“Breakups suck. But Rockstar exits are the worst,” she told her readers, claiming, “All I got was a five-minute phone call from him, after five weeks of calling and trying to get a hold of him because I just had to know if these rumors were true and hear it straight from the source.”

Basich insisted she got “nothing” from the Nirvana drummer turned Foo Fighters frontman, who “disappeared off the planet” in her world “but was everywhere else” because of his superstar status.

The multiple X Games winner said she “couldn’t avoid the thought of him,” even when running everyday errands.

“I went grocery shopping a few days after we broke up and heard the elevator music version of ‘Learn to Fly,’ which immediately made my stomach hurt. Then I saw him on the cover of Guitar Magazine staring at me in the checkout line,” she recalled, adding that she “didn’t know how to handle it” because she didn’t think she was “that strong.”

Representatives for Grohl did not immediately respond to Page Six’s request for comment.

On Tuesday, the musician revealed his indiscretion in a statement on Instagram.

“I recently became the father of a new baby daughter, born out of wedlock. I plan to be a loving and supportive parent to her,” announced Grohl, who has been married to his second wife Jordyn Blum since August 2003.

“I love my wife and my children, and I will do everything I can to regain their trust and earn their forgiveness.”

Grohl, who did not reveal the identity of his mistress, concluded his message by saying that he and his family are “grateful” for the public’s “attention” to all the children involved as they “move forward together.”

He and Blum, 48, who was last seen publicly looking happy at Wimbledon in London on July 2, have three daughters: Violet Maye, 18, Harper Willow, 15, and Ophelia Saint, 10.