Maier will work with Grass Roots Eventcom deputy chairman Graham Frazer to lead several major events projects.
"I see my role at Grass Roots as a rainmaker - a catalyst for a number of significant projects within the agency and for clients," said Maier. "I will also be involved with business development to ensure we are maximising our potential with all clients in all sectors."
Grass Roots head of global events Nick Bender said Maier and Frazer would create a "powerful team". " We have some exciting projects in development and I feel fortunate that Simon has joined us and am looking forward to working with him over the years to come."
Maier previously worked as an independent events and communications consultant. He has also held the post of Jack Morton Worldwide marketing director, Crown Communications chief executive and ICM UK managing director.
He recently co-authored a book, The 100 - Insights and lessons from 100 of the greatest speeches ever delivered, which is being serialised in The Times.