Alex Rodriguez appears to be Jennifer Lopez's biggest fan.

The 41-year-old former pro baseball player proudly shared video of his superstar girlfriend belting out her new single, "Ni Tu Ni Yo," at a house party on Tuesday, and also promoted the song on iTunes. Clad in a plunging white lace dress, J.Lo passionately sings into a mic in the video, as an excited onlooker shouts "sing" in Spanish.

"CANTA CANTA lol...El amor es asi... #lockerroommoment #nituniyo available on ITUNES tonight!!" Rodriguez wrote.

WATCH: Jennifer Lopez and Alex Rodriguez Heat Up the Dance Floor!

Lopez also shared a bit of her performance on Instagram, which included footage of Rodriguez filming her.

"You wanna be a part of this!!!" she wrote. "Don't miss the party... No te pierdas la fiesta!!! #NITUNIYO ON ITUNES AT 930pm!!!"

Capturing Lopez's picture-perfect moments is not new for Rodriguez. The athlete was also snapped intensely filming the Shades of Blue star on Friday during a taping of her Macy's 4th of July Fireworks Spectacular performance in New York City.

WATCH: Jennifer Lopez and Alex Rodriguez Show Major PDA in NYC

Late last month, A-Rod called dating Lopez a "humbling" experience during his appearance on the Tonight Show, admitting that people often mistake him for her security guard.

"When I was with the Yankees, and we won the world championship, and you wear the pinstripes, you think you're pretty cool," he told host Jimmy Fallon. "But then, you hang out with Jennifer, and they confuse me with the security guard all the time!"

"We were at the Met Ball, and the paparazzi were screaming at me, not even in English, 'Get the hell out of the way, get out of the way! We're trying to take a picture!'" Rodriguez added.

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