The couple went public with their romance in 2011, shortly after Lopez's split from ex-husband Marc Anthony.
Appearing on Good Morning America on Tuesday, Smart - a backing dancer - opened up about his relationship with the 42-year-old star.
"I don't think it was [love at first sight] for either of us," he explained. "It was just very natural how it happened. There was nothing before, no flirting, nothing."
Smart, who serves as chief choreographer on Lopez's current tour, also revealed his approach to working so closely with his girlfriend, adding: "Sometimes I tell her something, give her notes. But at the end of the day, you know, it doesn't matter what position is what, because she's the boss, you know?"
Lopez recently denied rumours that she and Smart are engaged and planning to marry in the near future.
> Jennifer Lopez buries bodyguard on beach with Casper Smart - Pictures
Watch Casper Smart discuss his relationship with Jennifer Lopez on Good Morning America below: