Charelli was raised in the Little Italy are of Ottawa near Preston St. His parents were wealthy entrepreneurs owning a number of stores in the neighbourhood. Robert was the youngest of their seven children.
Chiarelli was a excellent hockey player in High School and attended Clarkson University in New York State on a hockey scholarship. After graduation Chiarelli returned to Ottawa to attend the University of Ottawa law school.
Chiarelli became a noted lawyer and businessman in the Ottawa area before entering politics in 1980. In 1987, running for the Liberal Party of Ontario, he was elected as a Member of Provincial Parliament as the member for Ottawa West. He was reelected in the provincial elections of 1990 and 1995. Following the death of his wife in 1996, Chiarelli resigned.
In 1997 Chiarelli was elected as Regional Chair of Ottawa-Carleton. In 2000 the provincial government merged this position with that of the mayors of Ottawa and surrounding municipalities and Chiarelli decided to run for mayor of the newly amalgamated megacity.
Chiarelli was elected mayor on November 13, 2000, with the support of 56.3% of voters, replacing Jim Watson, who had decided not to run for reelection. He became the first mayor of the amalgamated city of Ottawa. Chiarelli won his second majority as mayor on November 10, 2003, with the support of 56.5% of voters. See 2003 Ontario municipal elections for election results.