The World Hockey Association wanted to put a team in Toronto, but in the league's first year Doug Michel owner of the planed team in Ontario could not reach a deal with Toronto Maple Leafs Owner Harold Ballard on a plan to share Maple Leaf Gardens. After initially considering Hamilton, the team ended up in the Ottawa Civic Center as the Ottawa Nationals.

The Nationals attempted to sign NHL stars Brad Park, Dave Keon, Eddie Shack and goalie Doug Favell, but were unable to land any of them, Coached by Billy Harris, the Nationals hosted the Alberta Oilers in the first ever game for the upstart WHA on October 11th, losing 7-4. The Nationals were the definitive middle of the pack team, ranking eighth in scoring and ninth in defense as they finished in fourth place with a record of 35-39-4, beating out the Quebec Nordiques by three points for the final playoff spot in the East.

The Nationals scoring attack was led by Wayne Carleton who led the team in goals (42) and assists (49). While Gilles Gratton and Les Binkley were the team's 1-2 punch in between the pipes.

During the playoffs the Nationals who averaged just over 3,000 fans a game in Ottawa, played their postseason games at the Maple Leaf Gardens as they faced the New England Whalers. The city of Ottawa demanded the team pay $100,000 to guarantee the club dates at the Ottawa Civic Centre, a price that Owner Dough Michel, who was already struggling financially balked at.

After dropping the first two games on the road, the Nationals scored a 4-2 win in their first game in Toronto. However, the Whalers would roar back to win the next game at MLG 7-3 as they won the series in five games.

The Whalers would go on to win the inaugural AVCO Cup Championship, while the Nationals stayed in Toronto and became the Toronto Toros.