The 52-year old was told on Wednesday night that he would be removed from his position.
He departs after seven seasons at the helm, finishing second last in 2019 and now set to miss the finals again in 2020.
He was expected to inform his players after Thursday’s captain’s run that his team at the club is over.
“I wish to thank the Dragons for allowing me to be head coach over the past seven seasons as well as everyone who has been involved in my journey at this proud club,” McGregor said in a statement on the club website.
“I approached the club’s chief executive Ryan Webb earlier in the week regarding a number of matters and we eventually came to an agreement that this week will be my last as coach of the Dragons.
“I understand a fresh face and new voice is needed to move the club forward. I hope this decision will provide clarity to the playing group, the entire staff and our passionate Red V members and partners regarding the direction the club is headed.
“After 25 years with the Illawarra Steelers and St George Illawarra as a player, staff member, captain and coach; I viewed my positions as a series of privileges not obligations.
“We haven’t met performance expectations over the past 18 months, and I take acceptance of responsibility. I had the opportunity to build my team, which we did in 2017 and 2018. Unfortunately, we have not put that same side on the field since for a number of reasons.
“Dean Young and the team have a fantastic opportunity over the next six weeks to build into the 2021 campaign. Dean deserves this great opportunity to showcase his capabilities in the head coach role.”
Dragons CEO Ryan Webb added: “The decision to part ways with Paul was one that nobody took lightly.
The Dragons face Parramatta at Bankwest Stadium on Friday night.