Talk about being “Blindsided.”

While Kelsea Ballerini and Morgan Evans’ divorce has resulted in a “he said, she said,” Page Six can exclusively reveal what allegedly happened before the former couple’s marriage fell apart.

An insider claims to us that the country-pop songstress cheated on her now-ex-husband with The Chainsmokers member Drew Taggart in August 2019 at Lollapalooza — after having collaborated on their hit 2018 track, “This Feeling” — but didn’t come clean about it to Evans until 2021.

We’re told the alleged affair, combined with other issues, led to Ballerini, 29, calling it quits with Evans, 37, last summer and “blindsiding” him with her decision.

A rep for Ballerini didn’t return Page Six’s requests for comment.

Both Taggart’s and Evans’ reps had no comment.

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Kelsea Ballerini allegedly cheated on Morgan Evans with Drew Taggart of The Chainsmokers (right), a source tells Page Six.drewtaggart/Instagram

The “Blindsided” singer filed for divorce from Evans in August 2022.morganevansmusic/Instagram

She cited “irreconcilable differences” as the cause of their split.Getty Images

A source close to Taggart, who recently has been linked to Selena Gomez, tells Page Six that the DJ, 33, was single at the time of his rendezvous with Ballerini.

Ballerini filed for divorce from Evans last August after nearly five years of marriage. Court documents obtained by Page Six at the time showed that she cited “irreconcilable differences” as the cause of their split.

Shortly before the “Just Married” singer’s interview on “Call Her Daddy” dropped late Tuesday, Evans took to Instagram to call out his ex-wife for not sharing the “reality” of their divorce, which was finalized in November.

“It’s really sad for me to see this person, who I spent so much of my life with, and loved with all my heart, saying things that aren’t reality and that leave out what really happened,” he wrote.

“She knows I’m not the type of guy to speak on those things publicly. If this is what she needs to heal, I hope it helps. All I ask is that if you’re on my pages, please don’t be mean. Don’t be mean to Kelsea, don’t be mean to each other.”

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Our insider claims Ballerini and Taggart hooked up at Lollapalooza in 2019.FilmMagic

“Life’s too short,” the “Kiss Somebody” crooner concluded his post.

During her bombshell-filled podcast appearance, the “Penthouse” performer detailed their “nasty” split and notably revealed that right before the CMA Awards in August 2019 — just weeks after her alleged infidelity — she and Evans had a blowout fight.

“There was, like, many a night of sleeping on the couch,” she told host Alexandra Cooper before recalling, “I slept on the couch the night before the CMAs, and I remember I went to rehearsal at the arena and texting him, and him being like, ‘I’ll see you at the carpet.’”

Ballerini had previously addressed the breakup after it became “public record” over the summer.

“I wanted you to hear from me directly that I am going through a divorce,” she began her statement at the time before calling the divorce a “deeply difficult decision” that was the “result of a journey of love, growth, and effort that ultimately has come to an end.”

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We’re also told the “Penthouse” songstress came clean about the alleged infidelity in 2021.morganevansmusic/Instagram

The “Half of My Hometown” singer noted that it was “hard to find words,” adding, “I feel extremely grateful for the many years of marriage to Morgan and hopeful for the next seasons.”

The Australian singer, for his part, kept his initial statement succinct.

“I am very sad to confirm that after almost 5 years of marriage, Kelsea and I are parting ways,” he wrote. “I wish it were otherwise, but sadly it is not.”

Taggart and Ballerini met when she collaborated with The Chainsmokers in 2018.Getty Images

Neither has commented on the allegations.Getty Images for iHeartMedia

Although Ballerini recently released an EP about her divorce, titled “Rolling Up the Welcome Mat,” Evans actually divulged about their breakup first in his song “Over for You,” which his ex described on “Call Her Daddy” as “opportunistic.”

“I felt really used in that moment,” she continued. “His healing journey is his healing journey. I respect that, but publicly exploiting that feels a little nasty to me before it’s final.”

Ballerini is currently dating “Outer Banks” star Chase Stokes.