Bignell joins the agency's TV department in the run-up to the negotiation season and takes on an external role dealing with media owners. He had previously worked alongside MindShare's investment director, Nick Theakstone, at MediaVest. Theakstone left to join MindShare last year.
As well as Bignell, Sabrina Booth has also been promoted within TV. She will focus internally on managing the investment department's relationship with the other divisions at MindShare. Both Bignell and Booth will report to the head of broadcast, Andy Zonfrillo.
Within press, both Vanessa Clifford and Tony Evans have been elevated from the role of business directors to become managing partners.
Clifford will concentrate on internal relationships, while Evans' primary focus will be external and both will report to the agency's head of non-broadcast, Paul Thomas.
All of the new managing partners will have senior client responsibilities.
Theakstone said: "These changes are about recognising and valuing some of the best people we have at MindShare, people who the industry acknowledges are highly talented, while making the department stronger and even more efficient. MindShare is committed to leading investment management and this structure will enable us to stay at the cutting edge."
The restructure follows the decision by MindShare's chief executive, Simon Rees, to leave the company earlier this month.