On the Provincial Diplomas, John G. Diefenbaker performs well and is in the top five High Schools in the CBE.

John G. Diefenbaker Senior High Schools' wrestling team is among the best in Alberta, having won seven city championships as well as five Provincial titles.

Its wrestling team was also the top ranked High School team in Canada in 2007, 2008 & 2009 according to the Canadian National Wrestling Association, having a large number of its members compete and obtain medals at the National Championships.

In addition, Diefenbaker has won city championships in girls' rugby, badminton, and in 2011 the Senior Girls Field Hockey team won the first ever Division 1 city championship against Western Canada beating them 1-0 in overtime.

[6] The Music Department holds two annual public concerts: one in the fall and one in the spring.