Doucet is a native of Bathurst, New Brunswick, Canada, where she grew up in an anglophone family. Her sister is Andrea Doucet, a Canadian Professor of Sociology. She has Acadian, Irish and Micmac ancestry. She graduated with a Bachelor of Arts degree from Queen's University at Kingston in 1980, where she wrote for the university newspaper. She gained a master's degree in international relations from the University of Toronto in 1982. The same year, she undertook a four-month volunteer assignment teaching English with Canadian Crossroads International in the Ivory Coast. She is currently one of the organisation's honorary patrons. Doucet speaks English and French, and is a less fluent speaker of Persian.
From 1983 to 1988, Doucet worked as a freelancer in West Africa for the Canadian media and for the BBC. This period proved a stepping stone to a longer term career with the BBC. Doucet reported from Pakistan in 1988, and was based in Kabul from late 1988 to the end of 1989 to cover the Soviet troop withdrawal and its aftermath. She was the BBC correspondent in Islamabad from 1989 to 1993, also reporting from Afghanistan and Iran. In 1994 she opened the BBC office in Amman, Jordan. From 1995 to 1999 she was based in Jerusalem, travelling across the Middle East. In 1999, she joined the BBC's team of presenters but continues to report from the field.
Doucet is often deployed to anchor significant news events from the field, and to interview key individuals. She played a leading role in the BBC's coverage of the "Arab Spring", reporting from Tunisia, Egypt and Libya. She has covered all major wars in the Middle East since the mid-1990s. Doucet has been a frequent visitor to Pakistan and Afghanistan since the late 1980s. Her work also focuses on the aftermath of major natural disasters, including the Indian Ocean tsunami in 2004 which took her to India and Indonesia.
In 2014 she made the documentary Children of Syria with film-maker Robin Barnwell, which was nominated in the Best Single Documentary category at the 2015 BAFTA Awards.
In 2015 she made the documentary Children of the Gaza War with film-maker James Jones.
Doucet has been a Council Member of the Royal Institute of International Affairs (Chatham House) and is currently a Council Member of the International Council for Human Rights (ICHR) based in Geneva. She is also involved with Friends of Aschiana UK which supports working street children in Afghanistan. Doucet takes pride in her ancestry and attends the Acadian World Congress which is held every five years. She notes that "It would be hypocritical to spend all my time learning about other tribes if I were to neglect my own".
Doucet won a Peabody and a David Bloom award in 2010 for her film on maternal mortality in Afghanistan, along with producer Melanie Marshall, Shoaib Sharifi and cameraman Tony Joliffe. She won Best News Journalist at the 2010 Sony Radio Academy Awards.
In 2002, she was the only journalist to accompany the Afghan president, Hamid Karzai, to his brother's wedding, where an assassination attempt was made. She and her team were later nominated for a Royal Television Society Award for their exclusive coverage of the attempt. Doucet last interviewed Ahmed Wali Karzai in April 2011, shortly before his assassination.
In 2003 she was awarded a Silver Sony Award for News Broadcaster of the Year for her interview with Yasser Arafat in his compound in Ramallah. In 2007, she was named International Television Personality of the Year by the Association for International Broadcasting. She also received the News and Factual award from the organisation Women in Film and Television.
Doucet has an honorary doctorate in Civil Law from the University of King's College in Halifax, Nova Scotia, an honorary Doctor of Letters degree from the University of New Brunswick (2006), an honorary Doctor of Laws degree from University College at the University of Toronto (2009), and an honorary doctorate in journalism from Université de Moncton.
In Britain, Doucet has received Honorary Doctorates from the University of York (2011), University of St Andrews (2014), and Liverpool Hope University (2015).
She was appointed Officer of the Order of the British Empire in the 2014 Birthday Honours for services to British broadcast journalism. She also received a Bayeux-Calvados Award for war correspondents.
In 2015, Doucet won the Sandford St Martin trustees’ award "for her commitment to journalism and her intelligent and clear reporting of the religious elements of global events".
At the 2017 International Media Awards, Doucet was awarded the Outstanding Contribution to Broadcasting Award. The award is given to journalists whose body of work has led to better understanding, and as a consequence increased prospects for peace.