The 29-year-old scored in four successive games in the month as the Cobblers moved out of the relegation zone.
O'Toole has been a key player for Northampton this season, his team winning seven of the 13 matches in which he has been involved.
"I'm really happy for John-Joe. He was brilliant for us in January and scored some very important goals," Northampton manager Jimmy Floyd Hasselbaink told the EFL website.
"It wasn't easy for him, we have had to nurture him through a little bit as he has continued his recovery from injury, and he has been playing with pain, but that just sums up his character and his will to do well for the team. He was a big factor for us in a good month and he deserves the award."
O'Toole added: "It feels great to be recognised for this award. We've picked up in terms of results in recent weeks so that's been great – apart from Saturday which was a bit of a kick in the teeth, so we need to get back to it, but we're heading in the right direction.
"It's been a bit of a difficult season for me personally injury-wise, and even when I got back in September it was frustrating being in and out of the team, but I've managed to get a run of games recently and managed to get on the end of a few which is nice but I want to get a few more now."