The couple, who refer to each other as "bear", sent sweet messages on the micro-blogging site Twitter to mark a full year since they first began dating, reported E! online.
"Casper Samar!!! BEAR!!!!!!!!!!!!!! Today is OUR's!! Thank you for sharing your beautiful smile with me everyday! ?Special Day. LOVE! (sic)," Lopez tweeted.
Smart, 25, replied, "Happy 1 yr anniversary to the most Gorgeous, Kind, Sweet, Funny, Beautiful Lil Bear in the world.... Love Bear. (sic)"
Lopez, 43, started dating backup dancer last year, four months after she and husband Marc Anthony called it quits after seven years of marriage. She has four-year-old twins Max and Emme with her former husband.