The 25-year-old is looking to reignite his career after being released from The Valley at the end of last season.
McLeod, a former England Under-21 international, recently underwent knee surgery and will not be fit for a few weeks.
Nevertheless, Bees chairman Tony Kleanthous told the club's official website: "This is a real coup and potentially one of our biggest signings."
McLeod added: "I am really looking forward to putting on a Barnet shirt, getting back to my best, playing football and scoring goals.
"I'll be kick-starting my career as soon as possible and I am enjoying it at Barnet but, at the moment, it is one step at a time and I'm working on my rehab."