The "On the Floor" hitmaker recreated Madonna's white lace dress and gloves look from her 1984 hit "Like a Virgin" for the October holiday, even donning an identical belt emblazoned with the phrase "Boy Toy."
And she insists there was nothing "odd" about her choice of costume for their small celebration at home because the 2008 relationship is all in the past.
Quizzed about her decision by U.S. media personality Andy Cohen on his Sirius XM show "Radio Andy", J.Lo laughed, "I mean, it was so long ago, so long ago. I don't know. No, it wasn't weird at all. I loved it."
She didn't share A-Rod's reaction to her costume paying homage to his ex, but reveals the couple and its pals had so much fun dressing up, her 12-year-old twins, Max and Emme, had no idea what was going on.
"We had like three friends over, four friends. And yeah, we all got dressed up like, way too much," the singer/actress confessed.
"My kids were like, hiding in the bedrooms. They were like, 'What are you doing?'"
J.Lo wasn't the only one taking her Halloween costume back to the old school - retired baseball ace Rodriguez did his best Bruce Springsteen impression circa 1984, donning a sleeveless denim jacket and bandanas around his neck, head, and wrist.