Tarek’s flip side.

Tarek El Moussa was cited for battery after the “Flip or Flop” alum allegedly knocked a man out in Las Vegas last week.

The HGTV star and another male were involved in an altercation at the Palazzo at the Venetian Resort in Sin City on June 5, the Las Vegas Metropolitan Police Department confirmed to Page Six Tuesday.

Witnesses alleged to TMZ, who was the first to report the news, that they saw El Moussa, 43, deliver a knee to the man’s head, which knocked him out cold.

An onlooker claimed to the outlet the incident was “bad,” adding that the guy looked seriously hurt. The alleged victim reportedly refused medical attention.

A source told Page Six that El Moussa was “protecting his elderly father” after the man allegedly got out of line with the real estate investor’s dad.

Cops arrived at the scene around 11 p.m. and took a crime report. Though they declined to arrest El Moussa, he was cited for battery.

A rep for El Moussa did not immediately respond to Page Six’s request for comment.

A few days ago, El Moussa’s wife, Heather Rae Young, shared snaps from their family Vegas trip on Instagram.

“Not our average Vegas trip… 🎰💎🖤,” she captioned the post. “Watched Tarek do his thing on stage (so proud!) and made it extra special by bringing our parents along for the ride.”

“We got to show them a glimpse behind the scenes — our world, our work, and of course, the glam. Grateful for these moments that we get to spend together. 🥂✨,” the former “Selling Sunset” star, 37, added.

Young did not mention the altercation.

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