The 27-year-old becomes the club’s second signing in 24 hours after French midfielder Malaury Martin joined on Tuesday.
Struna has joined until the end of the season following a three-year spell with Greek side PAS Giannina.
The 25-times capped Slovenia defender told his new club’s website: “I’m an attacking full-back and I think I’ll be a good fit based on the ideas presented to me by the club and the head coach.
“I like possession football and I understand that is the way Hearts want to play, so I am optimistic.”
Ian Cathro’s squad was earlier boosted by the signing of 28-year-old Martin.
The Frenchman signed a three-and-a-half-year contract after moving from Norwegian side Lillestrom.
The attacking midfielder previously played for Blackpool and Middlesbrough.
