The winger scored 27 goals in 132 appearances for Dundalk in three seasons in the Irish Premier League, including their final goal in their European campaign in Tel Aviv.
The Galway-born forward began his career at Salthill Devon, before turning professional in 2010. Since then, Horgan has played for Sligo Rovers before signing for Cork City in 2012 after a loan spell the previous season.
It was in 2014 that Horgan joined Dundalk where he went on to make over 100 appearances for the Lilywhites.
After attracting a lot of interest due to his exploits in the Europa League with the Irish side, Horgan chose Deepdale as his destination for his next challenge.
Horgan was called up by Martin O'Neill for the Republic of Ireland's World Cup qualifier against Austria, along with team-mates Andy Boyle and Aiden McGeady.
The 24-year-old signed a two -and-a-half year contract and made his Preston North End debut against Arsenal in the FA Cup third round at Deepdale when he came on as a 80th minute substitute.