With Clarkson's contract with Hawthorn coming to an end at the conclusion of next year, Mitchell is now set to lead the club following discussions this week.
As reported by Fox Footy's Tom Morris, Clarkson, Mitchell, CEO Justin Reeves and president Jeff Kennett met to discuss and confirmed the succession plan.
It is understood that Clarkson notified the playing group of the decision on Tuesday.
Mitchell has long been linked to succeed Clarkson after having strong support in the AFL community for a future in coaching at the highest level.
Clarkson today said that the decision was made with the best interests of the football club at heart.
“Understanding nothing lasts forever, the decision to finish my time at Hawthorn at the end of my current contract was the best path forward for the club long-term,” Clarkson told hawthornfc.com.au.
“We are all temporary custodians of the brown and gold, and we do our best to serve the colours well during our tenure.
“My philosophy has always been to give my assistant coaches the responsibilities and opportunities they need to achieve their career aspirations. Sam is on this journey and the period of transition between Sam and I provides further opportunity for him to develop as he prepares to step into the senior coach role.
"I am proud of what we have achieved as a club over the past 17 years."
Mitchell spoke of his excitement at the opportunity to keep developing the next crop of Hawks champions, and to continue working with the legendary coach for a little bit longer before taking over the top role himself.
“I am looking forward to continuing my work in developing our young crop of players and coaching the Box Hill side over the next 18 months,” Mitchell said.
“Development is an area of football that I am incredibly passionate about and I am confident that over the next 18 months we will continue to see more and more of what our young players are capable of."
Hawthorn president Jeff Kennett spoke of his admiration for Clarkson, and the impact he's had on the football club.
“To me, Alastair has always been a teacher and the most educated coach in the AFL, with a unique ability to infuse this wisdom among his players. Part of his role next year will be to better prepare Sam for his future responsibilities," Kennett said in a comment on the Hawthorn website.
“The Board and I see the same attributes in Sam. He is clearly ready to prove himself. Another year at Box Hill and continuing to work with Alastair before taking over the role at the end of next year will be the perfect preparation for him to step into the role of senior coach of our great club.
“Alastair sits in esteemed company alongside John Kennedy Snr and Allan Jeans as our most successful coaches. He will always be part of the fabric at Hawthorn.”