The 22-year-old started the season with league rivals Alfreton Town, but was released from the club recently by mutual consent.
Boro manager Kevin Wilson said: “Joe has been training with us and also played in a behind closed doors practice match where he did very well.
“He’s exactly the sort of player we are looking for – young, hungry and keen to do well for us. What’s more, he has a bit of strength, works hard and I’m confident he’ll score a few goals.”
The son of former Middlesbrough goalkeeper, Ian Ironside, Joe came through the youth set up at Sheffield United and was in the side that lost the 2011 FA Youth Cup final against Manchester United.
He joined Alfreton in January 2015 after being released by the Blades.
Ironside said: “I’m delighted to be joining the Boro and can’t wait to get started.
“I’m really impressed with the set up and the way the manager and his assistant go about things.
“I know a couple of the lads here and they speak very highly of the club and I’m really looking forward to helping the team push for promotion.”