The Cherries chairman, who has immersed himself in activity in the local community throughout his time at the club, takes up the role with immediate effect as he looks to ensure the club and its community counterpart work even closer together.
As a trustee Mostyn will be involved in all aspects of governance for the trust and will also be present at a number of its wide-ranging activities, offering his experience and guidance.
He will as part of his new role attend regular trustee meetings, to further enhance the close relationship between the football club and the Trust.
Mostyn is delighted to be more heavily involved with the Trust and hopes to be able to help a wide range of people in his new role.
“I have always loved going out into the community and ensuring that both myself and we, as a football club, give back,” he said.
“Within this role, I aim to harness the football club’s success to ensure we do all we can to have a positive impact on those in the local community.
“Steve and his staff do a fantastic job, touching the lives of so many people and it is a real honour to be involved in the great work they do.”
Head of the AFC Bournemouth Community Sports Trust Steve Cuss also added that he felt Mostyn’s involvement would be hugely beneficial to the club and wider community.
"Jeff has always been really interested in the community work and is a big advocate of the work we do,” he said.
“It’s a natural progression for him to take on this new role and it’s one he will embrace.
“We’re absolutely delighted - the experience, direction and support he can offer myself and the rest of the trust is crucial and he will be a massive role model at the events and schools.”