[1] At the age of thirteen, Sweet ran away from home and lived on the street for several months, eventually being caught and sent to St. Joseph's Training School in Alfred, Ontario.

He and wife, Almut, ran a tow truck business in Mississauga, Ontario from 1978 through the early 1980s and lead a real estate brokerage during the 1980s building boom.

In 2004, Sweet contested the nomination for the newly formed Conservative Party of Canada in the riding of Ancaster—Dundas—Flamborough—Westdale, defeating incumbent Liberal-turned-Conservative MP John Bryden.

[5] On June 22, 2006, Sweet obtained the unanimous consent of the House of Commons for a motion awarding honorary Canadian citizenship to the 14th Dalai Lama of Tibet, Tenzin Gyatso.

In the 2011 Canadian election, Sweet won re-election in the riding of Ancaster—Dundas—Flamborough—Westdale, winning more than double the votes of Liberal candidate Dave Braden.

On November 5, 2015, Sweet became the first elected Chair of the National Conservative Parliamentary Caucus, as prior to the 42nd Parliament the position was appointed by the party leader.

On November 29, 2019, Sweet was named Shadow Minister for International Human Rights and Religious Freedoms by then-leader Andrew Scheer.

In the House of Commons, Sweet focused on speaking to the importance of such a strategy and, during his speech, gave an account of the day that his daughter committed suicide.

"I share this painful and personal story to shed light on the importance of the initiative that the member from Timmins—James Bay is asking the House to consider, approve and undertake.

[18] He committed to advocating for increased funding for mental health research and programs, as well as promoting policies like the National Strategy on Suicide Prevention.

Though not an area of federal jurisdiction, Sweet has repeatedly called for the Government of Ontario to launch a public inquiry into so-called "training schools" like the one he was sent to as a child.

[19] In his letter, Sweet argued that an inquiry would bring forward recommendations on how to avoid similar injustices in the future, inform the public who he said "deserve to know what happened to their children with their tax dollars", and demonstrate the Ontario government's commitment to justice for those harmed by flawed policies and actions.

Sweet is an outspoken critic of Iran, which he has described as a state that "terror, supports terrorist groups like Hamas and Hezbollah, imprisons, tortures and executes their own people and others.

"[20] He has presented multiple petitions to the House of Commons calling upon the Government of Canada "to maintain the listing of the Islamic Republic of Iran as a state supporter of terrorism"[20] and has opposed any rollback of sanctions against the country.

Since then, the subcommittee has studied a wide variety of international human rights situations, including the situation Rohingya Muslims in Myanmar; child slavery and modern slavery; the persecution of Uyghur Muslims in China; the treatment of religious minorities in Pakistan; the protection of woman human rights defenders; and much more.

"[25] Sweet also attends annual Scleroderma walks in Hamilton and across Ontario to advocate for research to find a cure for the rare disease.

On September 19, 2017, Sweet rose in the House of Commons to deliver a Member's statement in Lara's memory, crediting her with reshaping his "thinking on whether someone has to have it all together to assist others".