The Northern Irish youth international has been freed by Boro - after failing to make the breakthrough at The Riverside Stadium.
Close had joined Northampton on trial last month, but now he has joined The Quakers.
Manager David Hodgson (pictured) has also kept striker Craig Russell at the club as cover, but he may not be a long-term squad member.
Meanwhile, goalkeeper Andy Collett has confirmed his retirement from the game.
The former Middlesbrough and Bristol Rovers shot-stopper has been with Darlington for four-and-a-half years, but a shoulder problem has now forced him to quit.
"I spoke to a specialist and he told me I had a 20 per cent chance of making a full recovery," said Collett.
"I was told that it would be a massive operation for a full-time goalkeeper to recover from.
"I'm devastated but with those kind of odds there was little point in me carrying on."
