Harrison will work with current first-team manager Carl Darlington, who was also his assistant at The Airfield during the Wingmakers' most successful season ever in the top flight of Welsh domestic football, before joining TNS in March 2010.
In addition, long-serving player Scott Ruscoe has been appointed as head of youth development and will also assist Harrison with first team duties on a day-to-day basis.
"Craig comes to us with a great football pedigree," said TNS owner Mike Harris.
"We were extremely impressed with his passion and professionalism during our interview process and we welcome him to the club."
A former Middlesbrough, Crystal Palace and Preston North End defender, Harrison was appointed manager of the Wingmakers at the beginning of July 2008, following the shock departure of Gareth Owen to concentrate on a playing career with Rhyl.
The Gateshead-born defender signed YTS forms with Middlesbrough as a 16-year-old teenager and was given his first team debut two years later by then manager and England legend Bryan Robson.
However, despite making an instant impact on the club's fortunes, Harrison's career was to falter after a catalogue of misfortunes.
A burst appendix kept him out of the game for 18 months and he then found his spot at left back occupied by Christian Ziege.
After enjoying a brief loan spell when David Moyes took him to Preston North End, he caught the eye of Crystal Palace manager Alan Smith who splashed £250,000 to take him to Selhurst Park.
But a double compound fracture ended his football career until a chance meeting with Owen at a surprise birthday party resulted in him succeeding Allan Bickerstaff as Owen's assistant at The Airfield in 2007.