Established as the Civil Service Savings and Loan Society, it was the first Canadian approach to cooperative banking outside Quebec.

[2] Alterna's major growth event was the 1 April 2005 merger between CS CO-OP and Metro Credit Union.

[5] Over the years it absorbed a variety of smaller credit unions, primarily ones that served universities, colleges or hospitals.

Alterna continues to operate a microcredit fund for disadvantaged Toronto entrepreneurs, and was one of the first financial institutions in Canada to perform regular social audits.

Alterna was one of the first financial institutions to make loans to businesses focusing on cannabis in Canada following its legalization, providing primary banking services for approximately two-thirds of the hundred licensed growers in 2018.