The 29-year-old has joined the League Two side until January 4 and will be available to make his debut this weekend against Accrington Stanley.
Northampton manager Aidy Boothroyd told Sky Sports News: "I'm delighted to bring in a proven goalscorer in Izale McLeod.
"He has always done well against my sides in the past, he will add another dimension to our attack and pose a real threat to our opposition.
"I'm really excited about working with him and I'm sure he will be a great addition to our squad."
Northampton are currently bottom of the League Two table.