The founding of the Princess Patricia's Canadian Light Infantry was undoubtedly in response to the unfolding events that led to the First World War. Captain Andrew Hamilton Gault, the founder of the Regiment, had the foresight to understand the severity of the situation in Europe, and the willingness to create an army unit that would be able to mobilize quickly in an international crisis. The creation of the PPCLI enabled Canada to expedite a military force overseas in 1914.

The growth of nationalism and imperialism throughout Europe during the early years of the twentieth century fashioned an atmosphere of conflicting political goals. Nationalism, combined with the creation of secret military alliances throughout Europe, fomented growing social and political upheaval. Shortly before Sunday afternoon, June 28th, 1914, the citizens of Sarajevo gathered to see Archduke Francis Ferdinand heir to the Austria-Hungary throne. As his royal touring car passed by the crowds, a young Bosnian student, Gavrilo Princip, assassinated both the Archduke and his wife. Austria-Hungary suspected that Serbia had approved the plot to kill Ferdinand, and declared war on Serbia. The balance of power that bound peace in Europe was broken, and the secret alliances of the international community came to light.

Canada's quick response to the war was due in part to the wealthy and distinguished Montreal businessman and Captain of the Royal Highlanders of Canada, Hamilton Gault. As a veteran of the South African war, Gault remained personally involved with the Canadian political responsibility to Britain as part of the Empire. As the climate of war overshadowed the international community in early August 1914, Hamilton Gault ventured by train to Ottawa with a proposal. He would personally raise and equip a mounted unit of Canadians for the Imperial authorities. The proposal was set in front of Colonel Sam Hughes, the Canadian Minister of the Militia and Defence. Colonel Hughes was attracted to the offer, but thought that an Infantry unit, as opposed to cavalry, would be more useful to Britain.

On August 4th, 1914, Germany's invasion of Belgium forced Britain into the war. As a loyal member of the Empire, Canada also declared war.

Great Britain's Declaration of War made Hamilton Gault's proposal even more credible to the Government. Lieutenant-Colonel Francis Farquhar, DSO, was an officer with the Coldstream Guards and Military Secretary to Canada's Governor General, His Royal Highness, the Duke of Connaught. He was enthusiastic about Gault's proposal, and knew the Government was seriously reviewing the idea. Farquhar and Gault decided that they should recruit men who had previous active service but were not obligated to militia units. LT. Colonel Farquhar approached the Duke of Connaught for permission to name the Regiment after his daughter, Her Royal Highness, Princess Patricia of Connaught. Princess Patricia had already become a much admired figure in Canada because of her appreciation of the country's vast wilderness and people. The request was made to the Princess, who was delighted. On August 6th, 1914, the Canadian Government provisionally accepted Hamilton Gault's offer.

Authority for the Regiment was granted on August 10th, through a charter embodied in a report of the Committee of the Privy Council of Canada, to raise and equip an infantry battalion. As detailed in the charter Hamilton Gault would contribute $100,000 to finance and equip the battalion with the remainder of expenditures being covered by the Department of Militia and Defense.

Mobilization of the Princess Patricia's Canadian Light Infantry progressed quickly. The recruiting project began on August 11th and was completed eight days later as veteran soldiers flocked to Ottawa from every part of Canada. The recruitment campaign extended to six cities: Montreal, Toronto, Ottawa, Winnipeg, Calgary and Edmonton. By August 19th 1,098 ranks had been accepted from 3,000 applicants, and of them 1,049 had seen previous service throughout the British Empire. It is said that all but one unit in the British Army was in the ranks of the new Regiment, as well as men from the Royal Navy and Marines.

The Regiment's first formal parade was held on August 23rd. Princess Patricia presented her Regiment with a Camp Colour that she had designed and worked by hand. On it, the initials "VP" (Victoria Patricia) in gold were entwined upon a blue center on a crimson background. The "Ric-A-Dam-Doo", as it later became known to all Patricia soldiers, was affixed to a staff cut from a Government House maple tree. The Colour was carried into every battle in which the Regiment fought in the First World War. The Edmonton City Pipe band traveled to Ottawa under the leadership of Pipe-Major C. Colville, a veteran who reported for duty in Hunting Stewart Tartan and announced to the Commanding Officer that "We came (Sir) to pipe you to France and back again".