The 29-year-old’s current contract was due to expire in the summer.
Hamilton boss Billy Reid said: “Alex has signed for three years with the club which is fantastic news. It is a big boost for me and the club.
“He has been here six years and over the last couple of days we have been speaking to him about a new contract.
“There were other teams interested so I am delighted that our leader and captain is staying another three years.
“Without being disrespectful to any other player he has been my best signing.”
Neil said: “I am over the moon.
“What excites me is playing alongside young kids.
“There is nothing better when you have a young player next to you who is keen to learn from you.”
