Tumilty, 25, joins on a free transfer after leaving Scottish Championship side Raith Rovers at the end of the season.
Tumilty becomes Hartley’s second signing since being appointed as Pools’ new boss after the signing of goalkeeper Kyle Letheren.
Speaking on his arrival at the Suit Direct Stadium Tumilty said: “I’m delighted to sign for Hartlepool United. This is a great opportunity to play in the EFL and also work with Paul once again.
"When I was aware of the interest, there was only one club I wanted to sign for. I have seen videos and photos of how great these fans can be and I can't wait to get started.”
Pools boss Hartley also commented on the move outlining Tumilty’s versatility as one of the key factors in bringing him to the Suit Direct Stadium.
"Reghan is someone I've worked with before. He’s a great character and hungry for success.
"He can play in multiple positions which gives us great options. He works hard and we are looking forward to getting him involved with a busy few weeks of pre-season to come.”