The agency was founded on November 1, 1999 by Chris Staples, Ian Grais and Tom Shepansky. All three were formerly employed at Palmer Jarvis DDB (now DDB Vancouver). Staples was the national creative director of that agency; Grais was the creative director and Shepansky was the director of client services.
Staples, Grais and Shepansky opened Rethink with no staff and no clients. In December 1999 they won the Dominion Grocery Store account in Ontario and the A&W Food Services account nationally, in English and French.
In their first year of operation the agency grew to 20 people and was featured on the CBC-TV business program Venture. Rethink made news by offering a money-back guarantee in the form of a five percent rebate to be earned based on client-set criteria. They also launched Rethink Beer to demonstrate their branding abilities. The product was available in BC and Alberta until 2003.
The agency currently handles advertising, design and online work for a range of local, regional and national clients. These include A&W (Canada),  Shaw Communications, Molson Coors Brewing Company, Coast Capital Savings, Mr. Lube, Playland, Science World at TELUS World of Science, and Weston Bakeries.
The agency was also ranked by Strategy Magazine as the most award-winning agency in Canada in 2008 and 2009. Partners and co-creative directors Staples and Grais were ranked the most awarded creative directors in 2006, 2008 and 2009 in the same surveys.
On April 5, 2010 Rethink opened an office in Toronto, headed by partner and managing director Pema Hegan and creative director Dre Labre.
- Chong, Kevin (3 June 2009). "Chris Staples of Rethink Advertising Reimagines Vancouver Advertising". BC Business. Vancouver.
- Hunter, Jennifer (22 November 1999). "Shaking up the ad world". Maclean's Magazine. Toronto.
- Lazarus, Eve (24 March 2003). "Dynamic Duo". Marketing Magazine. Toronto.
- "Venture (CBC)". Venture. Season 17. September 1, 2001.
- Folb, Mikala (26 November 1999). "The ad lib". Canadian Business Magazine. Toronto.
- Prendiville Roux, Julie (May–June 2007). "Rethink". Communication Arts.
- Williams, Natalia (December 2006). "The Rethink Effect". Strategy Magazine. Toronto.
- Toane, Carey (February 2009). "Top agency: Rethink thinks local, wins big". Strategy Magazine. Toronto.
- Lazarus, Eve (24 November 2003). "Rethink's Fresh Obsession". Marketing Magazine. Toronto.
- "Top Agency: Rethink". Strategy Magazine. Toronto. February 2008.
- Williams, Natalie; Spevick, David (February 2006). "Top Creative Directors: Ian Grais, Chris Staples, Rethink". Strategy Magazine. Retrieved February 2006. Check date values in:
- "Top Creative Directors: Rethink's Chris Staples and Ian Grais". Strategy Magazine. Toronto. February 2008.
- Toane, Carey (February 2009). "Top creative directors: Ian Grais and Chris Staples of Rethink". Strategy Magazine. Toronto.
- "Coast Capital Savings wins BCAMA 'Marketer of the Year' Award" (Press release). Coast Capital Savings. 18 July 2006. Retrieved 18 July 2006.
- "Mr. Lube wins marketer of the year". The Vancouver Sun. 25 June 2008.