The Red Ensign bearing some sort of a Canadian emblem was used by Canadians both on land and at sea beginning as early as 1868 (soon after Confederation) on an informal or extra-legal basis. As Prime Minister, Sir John A. Macdonald "constantly made use of it", promoting it throughout Canada "by precept and example." An 1891 memo from the Governor General, Lord Stanley, stated: "the Dominion Government has encouraged by precept and example the use on all public buildings throughout the provinces of the Red Ensign with the Canadian badge on the 'Fly.'" In 1892, it was authorized by Admiralty Warrant for use on ships registered in Canada and this was enshrined in the Canada Shipping Act of 1934, yet the flag had no legal status on land (the Royal Union Flag remained the formal national flag of Canada until 1965). Despite its lack of any official status on land, the Red Ensign with Canadian arms was widely used on land, and flew over the Parliament Buildings until 1904 when it was replaced by the Union Flag. Various versions of the Red Ensign continued to be flown on land and the flag featured prominently in patriotic displays and recruiting efforts during the First World War. It can be seen in numerous photographs of Canadian troops, on the prime minister's car, and in victory parades.

The original Canadian Red Ensign had the arms of the four founding provinces on its shield. However, in the late 19th and early 20th century, flag manufacturers would often supplement this design with wreaths of laurel and oak leaves and crowns. The design was frequently placed on a white background square, circle or roughly following the outline of the arms in the flag's fly (right hand side assuming the flagpole to be on the left). There was no standard design for the Red Ensign until the early 1920s. In 1921, the Government of Canada asked King George V to order a new coat of arms for Canada. The College of Arms thus designed a suitable coat of arms of Canada. The new shield was formally adopted on the Canadian Red Ensign through order-in-council on 26 April 1922. In 1924, the Red Ensign was approved for use on Canadian government buildings outside Canada. The Canadian Red Ensign, through history, tradition and custom was finally formalized on 5 September 1945, when the Governor General of Canada signed an Order-in-Council (P.C. 5888) which stated that "The Red Ensign with the Shield of the Coat of arms in the fly (to be referred to as "The Canadian Red Ensign") may be flown from buildings owned or occupied by the Canadian federal Government within or without Canada shall be appropriate to fly as a distinctive Canadian flag." The flag was thus approved for use by government buildings inside Canada as well, and once again flew over Parliament.

The Red Ensign served as the country's civil ensign from 189…

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Though much less common than either the Maple Leaf or modern provincial flags, the several versions of the Canadian Red Ensign continue to be flown today both in official and unofficial capacities. In view of its association with the Canadian Army during the world wars, it is flown alongside the Maple Leaf flag at numerous war memorials, including the Canadian National Vimy Memorial in France. It is also used by veterans' groups, and is part of the official colour party (together with the Maple Leaf) of the Royal Canadian Legion. The flag is sometimes flown on vintage ships, and at heritage sites where it is historically accurate.

In the 2010s, some far right, white nationalist or white supremacist groups co-opted the red ensign, displaying it either alongside or instead of the Maple Leaf as a symbol of a monoculturally white Canada. These include the Aryan Guard, the founder of the Canadian Nazi Party, white nationalist leader Paul Fromm, and the five members of the Proud Boys who disrupted an indigenous protest on Canada Day in July 2017.

The flag's appropriation by white supremacists has produced an outcry from several groups, including the Royal Canadian Legion, the Canadian Centre for the Great War, and the editor of the history journal The Dorchester Review, who have expressed the view that "trivializing, or treating as a kind of talisman of defiance, a flag that has a much more venerable and mainstream role" is not right and "flies in the face of what the Red Ensign means".

Before the adoption of the new arms of Canada in 1921, flag makers made the badge larger each time a new province joined Confederation. This led to the creation of several unofficial but widely used variants of the Canadian Red Ensign.

At the opening ceremony of the 1936 Olympic Games, a variant of the 1922–1957 red ensign with the arms inside a white disc was carried by Canadian Olympian and flag bearer James Worrall. However, the normal version of the red ensign without the disc was hoisted alongside the other national flags that surrounded the perimeter of the stadium.

Some of the variations are shown below.
• 1868: The Canadian Red Ensign used at July 1 Dominion Day celebrations in Barkerville, BC in support of Canadian Confederation, as Canada did not have an official flag.
• 1870: An early version of Manitoba's coat of arms was added to represent the new province.
• 1870: Until 1922, there were variations in displaying the shield on the flag: sometimes a white disk was added behind the shield, sometimes there would be a wreath of maple leaves or a wreath of roses, thistles, and shamrocks, and occasionally the shield was topped by a beaver or crown.
• 1871: Symbols were added to represent British Columbia. This version was rarely used and was overshadowed heavily by the 1868, 1870, and 1873 versions, all three of which remained in use until the early 1900s, while the 1871 version was never particularly common.
• 1873: The flag was modified to represent the new provinces of British Columbia and Prince Edward Island. The badge was always placed on a white disk in this edition.
• 1896: British Columbia adopted a new coat of arms.
• 1907: Alberta and Saskatchewan were added to the flag. The coats of arms of British Columbia, Prince Edward Island, and Manitoba took on their modern forms.
• Flag with 1922-1957 disc. The flag was carried by James Worrall at the opening ceremony of the 1936 Olympic Games.
• Flag with 1957-1965 disc
• Flag of the lieutenant governor of Ontario from 1959 to 1965, the 1957 Canadian Red Ensign with the shield of Ontario below the Union Flag.
Today, two Canadian provincial flags are Red Ensigns, the flag of Ontario and the flag of Manitoba. In 1965, after the Great Flag Debate in Parliament and throughout the country as a whole, t…

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