Mayer began his career in 1986 when he was named assistant to the Director and later assistant director of the 49th Parallel Centre for Contemporary Canadian Art in New York (1986-1990). He was Head of Visual Arts with the Cultural Services of the Canadian Embassy and a correspondent for the New York periodical
Rizzoli’s The Journal of Art in Paris (1990-1993). Afterwards, he served as the curator of the
Albright-Knox Art Gallery in
Buffalo, New York (1994-1998). From 2001 to 2004, he served as the deputy director at the
Brooklyn Museum in
New York City and then as director of
The Power Plant in
Toronto (1998–2001). During his tenure as director and CEO, he helped with many large-scale acquisitions such as James Hart's outdoor sculpture,
The Three Watchmen and other works which he sited on Nepean Point hoping to begin a "precinct of beauty" in the capital, as well as co-curating the
Jack Bush exhibition (2014), and overseeing numerous projects including the creation of the Canadian Photography Institute. He worked to increase the recognition of indigenous work and oversaw the opening of the Canadian and Indigenous Galleries in June 2017. Also that year, Mayer published
Art in Canada, a book that celebrated Canadian and Canadian Indigenous artists. It was released to coincide with Canada's sesquicentennial. The book, designed by Paprika, won third prize in the Pictorial category for the 36th annual
Alcuin Society Awards for Excellence in Book Design in Canada (2017). In 2020 he appeared as a judge on
Landscape Artist of the Year Canada. Mayer was appointed to the
Order of Canada in 2022, "for his contributions to fine art as an administrator and curator, both in Canada and worldwide." ==Controversy==