Lamar, who's notoriously tight-lipped about his private life, called Alford his "best friend" in an interview with Billboard in January.
"I wouldn't even call her my girl," he said. "That's my best friend. I don't even like the term that society has put in the world as far as being a companion -- she's somebody I can tell my fears to."
Clearly, he's not afraid to show his silly side with his fiancée. Check out the two playing dress up last Halloween, celebrating in Puerto Rico.
It's definitely an exciting time for Lamar -- He won a Grammy for best rap performance in February, and last month he released his critically acclaimed third studio album, To Pimp a Butterfly, which earned him his first No. 1 album on the Billboard charts.