Mr. O'Brien is Chairman of the privately-owned telecommunications company Digicel Group.
Denis has a wide number of investments in several sectors including media, property, leisure and industrial services. He is a former recipient of the Ernst & Young Entrepreneur of the Year Award. In 1989, Denis founded Communicorp , an Irish media holding company. He founded the Esat Telecom Group and built it throughout the 1990s until its sale to British Telecom for €2.4bn. In 2001, Denis started Digicel, a telecommunications company, in Jamaica. Since then, Digicel has grown to serve over 30 markets around the world.
Outside of his extensive business interests, Denis chaired the 2003 Special Olympics World Summer Games in Ireland. He is a director on the US Board of Concern Worldwide and a member of the UN Broadband Commission for Digital Development. He also chairs the Clinton Global Initiative Haiti Action Network. In addition, he is the Chairman and Co-Founder of Frontline, the International Foundation for the Protection of Human Rights Defenders, which is based in Dublin.
In 2000 he established The Iris O’Brien Foundation to identify and assist projects in Ireland and internationally which aim to alleviate disadvantaged communities. Denis is also the patron of the Digicel Foundation, which supports communities in Jamaica, Haiti, Papua New Guinea and Trinidad & Tobago. In 2019, Denis received the Award for Outstanding Achievement from the Ireland-US Council to recognise his career and achievements in building relationships between the United States and Ireland.
Denis holds a BA degree from University College Dublin and an MBA from Boston College. In 2015, Denis established the O'Brien Fellowship at Boston College , an annual grant awarded to two Irish students to help them pursue an MBA.