Horgan has spent the last 18 months at Deepdale after leaving Irish football for England, but just 12 starts and 28 substitute appearances have been made in the Championship.
That had resulted in the 26-year-old being left on the fringes of Alex Neil's squad, and Hibernian have moved to hand the attacker a fresh start in the Scottish Premiership.
Horgan told the club's official website: "I am delighted to have made the move to Hibs. I've spoken to the manager [Neil Lennon} and am excited for his plans for the season ahead.
"Obviously the boys have started well in Europe and the league - they had a good season last year and the ambition is there to follow that up with another successful year. I'm ready to play and looking forward to trying to break into the team."
The Republic of Ireland international has penned a three-year contract at Easter Road.