The former assistant is promoted ahead of the departure of David Ripley at the end of the season
John Sadler will replace David Ripley as Northamptonshire head coach at the end of the season.
The 39-year-old has served as assistant coach since December 2019 and previously had spells with Derbyshire and Leicestershire, whom he represented during his 11-year professional playing career.
Bowling lead Chris Liddle will also take on the role as assistant coach.
"I’m absolutely delighted to be stepping into the top job," said Sadler.
"I feel the club is in a really good place and ready to kick on even further.
"We’ve got a very exciting group of cricketers and some great people around so it’s an exciting opportunity to take on."
He added: "I’m sure things will be slightly different with a different voice and different ideas but ultimately there’s been some brilliant things going on here so it’s about adding to those and not necessarily changing too much."
Chief executive Ray Payne explained: “When we brought John on board at the end of 2019 there was always a feeling that he was someone we wanted to keep around long term.
"He’s been an excellent addition to the club and I’m looking forward to seeing what he can do as our head coach.”