Jared Cowen is a product of the Spokane Chiefs of the Western Hockey League and was selected ninth overall by the Ottawa Senators at the 2009 NHL Entry Draft. He made his NHL debut with the club on April 8, 2010 in a game against the Tampa Bay Lightning following the Chiefs elimination of the WHL playoffs.
Born in Saskatoon, Saskatchewan, Cowan was honoured to be chosen to Canada's junior team for 2010 World Junior Championships being held in Regina. The huge defenceman would help the Canadian squad to a silver medal in the tournament.
The 2011-12 season would be Cowan's first full professional campaign. In 82 games for the Senators he would score five times and add 12 assists while acclimatising himself to life as an NHL defenceman.
A hip injury cut Cowan's 2012-13 season short. He would appear in just three games in the American Hockey League and seven in the NHL. Cowan would return the following season and would appear in 68 games for the Senators, recording 15 points and 45 penalty minutes. Injuries again slowed Cowen down in 2014-15. He appeared in just 54 games for the Senators and struggled to find his game.
On February 9, 2016, Cowen's time in Ottawa would come to an end. He was shipped to the Toronto Maple Leafs as part of a nine-player trade that saw the Senators acquire Dion Phaneuf amongst others.