Jenkins joins Pools after leaving Championship club Middlesborough earlier this month, writes Tom Feaheny.
While he mainly worked in the academy, he also assisted Steve Agnew at first team level during the latter part of last season.
Speaking to the club's website about the appointment, Harrison said: “We’ve known each other a long time which is important but just as crucial is to have a young and dynamic team because energy and enthusiasm will play a huge part and we have that in all members of our staff.
“The quality he has and the delivery on the pitch as well as the support he can offer me is going to be unbelievable because he has been there and done it at all levels, from under 9s up to working with the first team in the last few months of last season.
“He has a broad range of experience and skills but he also has all the qualities I want so I am sure the lads will work hard but also enjoy training with him as much as they have at any of their others clubs.”