Ms. Marcoux is Chair of the Board of Transcontinental Inc. since 2012, a leader in flexible packaging in North America and Canada’s largest printer and a leader in school textbook publishing. Previously, she was Vice Chair of the Board from 2007 to 2012 and Vice President, Corporate Development from 2004 to 2012.

Between 1998 and 2004, she held the successive roles of Director, Legal Affairs and Assistant Corporate Secretary, and Director, Mergers and Acquisitions. Before joining Transcontinental Inc., she was a lawyer at McCarthy Tétrault LLP.

Ms. Marcoux is a member of the board of Rogers Communications Inc. She was also a member of the board of George Weston Limited for 12 years, until 2019. Moreover, Ms. Marcoux sits on the board of the Institute for Governance of Private and Public Organizations (IGOPP) and is a member of its Governance and Ethics Committee, in addition to being a member of the board of Scale AI. Since January 2021, she is the Honorary President of the Major Donors Circle of Centraide of Greater Montreal, which she chaired from 2018 to 2020, was co-chair of the 2016 Centraide of Greater Montreal campaign and co-chaired the 2015 Leaders’ Circle campaign. In addition, she is a member of the board of The Montreal Children's Hospital Foundation since 2015 and the Advisory Board of McGill University’s Law Faculty since 2018. She has also been involved in several fundraising campaigns, notably for the Montreal Museum of Fine Arts, the Montreal Heart Institute, the Tel-Jeunes Foundation, the Young Musicians of the World Foundation and the Foundation Montréal inc.

In 2016, Ms. Marcoux was awarded the Medal of the National Assembly of Québec and, in 2017, she became the first Canadian to win the Visionary Award for Strategic Leadership from the global organization Women Corporate Directors Foundation. Also in 2017, she was inducted into the Women's Executive Network (WXN) Hall of Fame, after being named one of Canada’s 100 most powerful women by the organization in 2010, 2012 and 2016. In 2019, she was appointed Member of the Order of Canada.

Ms. Marcoux holds a Bachelor’s degree in Political Science and Economics, and a Bachelor’s degree in Civil Law, both from McGill University. She has been a member of the Québec Bar since 1995.