Oshawa, Ontario: Demographics, Community & Neighborhoods. Population According to 2011 census, population of Oshawa is 149,607 which is increased from 141,590 (5.7%) within 5 years. In 2001, 50.7% of the population was female, while 49.3% was male. Approximately 6.5% of the population of Oshawa was under five. This is percentage is high as compared…