The striker signed after John Still got the man he really wanted.
Harrison returned to London permanently after a loan spell at Sutton United last season. He was a Barrow player before that but now he is back in the capital.
Manager Still says just because there is only a week to go until the season starts that people shouldn’t think he wasn’t the Bees’ first choice.
“He's always been a goalscorer,” Still told the club’s website. “When the situation with John (Akinde) was going on, we highlighted two or three people and Byron was top of our list.
"I think he needs little introduction because he's known a lot around this level for being a goalscorer so he's ideal for us."
Barnet open up against Aldershot on August 4 in an exciting first day fixture.
Harrison said: "Every player wants to be wanted, especially strikers. You want to feel like your manager has got full faith in you and that's how you work at your best.
"I know what the pressures will be, I'll be expected to lead the line in a team that will be looking to push to get back into the Football League. I'll be hoping to score goals to help Barnet push on."
He wasn’t the only new arrival at The Hive on Friday.
Talented 28-year-old midfield man Medy Elito became their tenth arrival of the summer, signing a two-year deal.