Forward Zack Newton has joined from National League South-outfit Welling United, while midfielders Jared Rance and Lea Dawson have been signed from Bostik South East-sides Burgess Hill Town and Cray Valley Paper Mills.
Goalkeeper Josh James, also acquired from Burgess Hill Town, has come back to the Hornets for a second spell at the club, filling the hole left by Josh Pelling's departure.
Speaking to horshamfc.co.uk Horsham boss Dominic Di Paola said: “We didn’t want to bring in loads, we just wanted to strengthen because we were a bit light at the end of last season.
“They add a bit of experience, a bit more mobility, in and around the group, which is good, so we’re just going to see how we go really.”
Newton, who has also spent time at Metropolitan Police and Worthing, revealed that the Hornets' new Hop Oast facilities and speaking to Di Paola drew him to joining the club.
The midfielder, also speaking to the club's website, added: “I think it’s just the new facilities essentially. It’s a new team coming up and there are a lot of prospects.
“I had a chat with Dom, and he mentioned a lot of good things about where the club wants to go, so I’m willing to try out with him and go forward with the club.”
Dawson was a member of the Cray Valley Paper Mills squad who reached last season's FA Vase final. Prior to his move to Cray Valley in January, the midfielder made 19 appearances and scored once for Ashford United in the Bostik South East in 2018/19.
Rance is another ex-Worthing player. Mackerel Men boss Adam Hinshelwood made the midfielder one of his first acquisitions after arriving at Woodside Road in 2017, but a lack of first team chances saw Rance leave for Burgess Hill.
Returning goalkeeper James joined the Hornets in June 2017, but left three months later after deciding to take a break from football.