He was first elected to Metropolitan Toronto Council for Scarborough-Malvern in 1991, and was re-elected in 1994. After the Scarborough and the other suburbs were amalgamated into the new City of Toronto, Cho was elected to the new council representing Scarborough-Malvern in 1997 along with Bas Balkisson. In 2000, he was again re-elected and now represents the new ward of Scarborough Rouge-River. He won re-election in 2003 and 2006.
Cho was Chairman of the Toronto Zoo for two successive terms.
Cho was a New Democratic Party candidate for election to the Canadian House of Commons in the 1988 federal election and was initially identified as a New Democrat when he joined Metro Council, however, he soon became an ally and supporter of then Metropolitan Toronto Chairman Alan Tonks and dropped his NDP affiliation. He subsequently took out membership in the Liberal Party though, like most non-NDP municipal politicians in Ontario he did not run on a party label in municipal elections.
He ran in the 2004 federal election as an independent candidate in Scarborough—Rouge River. Cho called himself an "independent Liberal", and used the Liberal Party of Canada's red-and-white colours for his campaign materials. He was accused of trying to mislead voters by the official Liberal candidate, Derek Lee. Lee won the election, although Cho placed a respectable second with 6,692 votes 17.8% of the total), ahead of the candidates of the other three main parties, the Conservative Party, the Green Party of Canada, and the New Democratic Party.
On August 13, 2004 The Toronto Star reported in a headline that "Cho misused funds, colleague charges Councillor accused of using city money for federal election campaign". In May, the month the federal election was called, reports showed that Mr. Cho expensed $21,156 in costs, which helped pay for a newsletter and fridge magnet that was sent to 22,000 households in his Scarborough-Rouge River ward.
In 2005, Cho expressed interest in being the Ontario Liberal Party's candidate in the Scarborough—Rouge River provincial by-election which was made necessary by the appointment of incumbent Liberal MPP Alvin Curling to a diplomatic position. However, the Liberal riding association used a clause of its constitution to declare Bas Balkissoon, City Councillor for Ward 41 (the part of Scarborough—Rouge River not represented by Cho), as its candidate without a contested nomination battle. Media reports suggest that this was done to exclude Cho as the provincial riding association was displeased with Cho's "independent Liberal" candidacy in the aforementioned federal election. Though the provincial and federal Liberal parties have overlapping memberships, they are separate entities and Cho could not simply be denied membership in the provincial party for offending the rules of the federal organization. Cho was displeased with the Liberal riding association's decision and as a result, he campaigned for the Progressive Conservative candidate, Cynthia Lai, in the by-election as seen by a volunteer for the New Democratic Party Campaign.
Cho holds a Masters' degree in Social Work and Doctorate in Education from the University of Toronto.
He is married to Soon-Ok Cho, and has three adult sons.