In August 1828 Colborne was appointed Lieutenant Governor of Upper Canada.
As Lieutenant Governor, Colborne increased the population of the province by 70% by initiating an organised system of immigration to bring in settlers from Britain.
He also aided settlement by expanding the communication and transportation infrastructure through a campaign to build roads and bridges.
He brought changes to the structure of the legislative council, increased fiscal autonomy and encouraged greater independence in the judiciary.
In 1829 he founded Upper Canada College as a school based on the Elizabeth College, Guernsey model to educate boys in preparation for becoming leaders of the colonies.

During Colborne's period of office as commander-in-chief, the Family Compact promoted resistance to the political principle of responsible government.
At the end of its lifespan, the Compact would be condemned by Lord Durham as "a petty corrupt insolent Tory clique".
In both Upper Canada, which was under Colborne's administration, and Lower Canada, which was under the direct administration of Colborne's superior, Governor General Lord Gosford, this resistance to responsible government, together with conflicts between the assembly and the executive over fiscal matters, as well as a difficult economic situation, led to the Rebellions of 1837.

In January 1836 Colborne became commander-in-chief of all the armed forces in British North America.
He was promoted to the local rank of lieutenant general on 8 July 1836.
 Colborne personally led the offensive at the Battle of Saint-Eustache in December 1837 defeating the rebel force which had become holed up in a church.

Colborne was advanced to Knight Grand Cross of the Order of the Bath on 29 January 1838.
Following Lord Gosford's resignation in February 1838, he became acting Governor General of British North America.
In Lower Canada but not Upper Canada, the 1791 constitution was suspended at this time, causing the colony's bicameral parliament to be dissolved.
To replace these bodies and assist in governing Lower Canada, Colborne established a 24-member Special Council.

Colborne stepped aside as acting Governor General until the arrival of Gosford's formal successor, Lord Durham, on 27 May 1838.
Colborne was promoted to the substantive rank of lieutenant-general on 28 June 1838.
Durham remained in Canada only for a few months, resigning on 9 October and leaving for London on the fifth-rate HMS Inconstant on 1 November, after he learned that his policy of leniency towards the leaders of the prior year’s rebellion had been repudiated by the British Government.
Durham's departure caused Colborne to again become acting Governor General.
Colborne put down a second revolt in November and was confirmed as Governor General of British North America on 14 December.
He left Canada in October 1839 after the arrival of his successor, Charles Poulett Thomson (who shortly thereafter  would be elevated to the peerage as Lord Sydenham).
After arriving back in England, Colborne was himself elevated to the peerage as Baron Seaton, of Seaton in the County of Devon, on 5 December 1839.

In recognition of the "important services" rendered by Colborne, and following a message from Queen Victoria, Parliament settled an annuity of £2,000 on him and the next two heirs male who would succeed to the title.
In August 1828 Colborne was appointed Lieutenant Governor of Upper Canada. As Lieutenant Governor, Colborne increased the population of the province by 70% by initiating an organised system of immigration to bring in settlers from Britain. He also aided settlement by expanding the communication and transportation infrastructure through a campaign to build roads and bridges. He brought changes to the structure of the legislative council, increased fiscal autonomy and encouraged greater independence in the judiciary. In 1829 he founded Upper Canada College as a school based on the Elizabeth College, Guernsey model to educate boys in preparation for becoming leaders of the colonies.
During Colborne's period of office as commander-in-chief, the Family Compact promoted resistance to the political principle of responsible government. At the end of its lifespan, the Compact would be condemned by Lord Durham as "a petty corrupt insolent Tory clique". In both Upper Canada, which was under Colborne's administration, and Lower Canada, which was under the direct administration of Colborne's superior, Governor General Lord Gosford, this resistance to responsible government, together with conflicts between the assembly and the executive over fiscal matters, as well as a difficult economic situation, led to the Rebellions of 1837.
In January 1836 Colborne became commander-in-chief of all the armed forces in British North America. He was promoted to the local rank of lieutenant general on 8 July 1836.  Colborne personally led the offensive at the Battle of Saint-Eustache in December 1837 defeating the rebel force which had become holed up in a church.
Colborne was advanced to Knight Grand Cross of the Order of the Bath on 29 January 1838. Following Lord Gosford's resignation in February 1838, he became acting Governor General of British North America. In Lower Canada but not Upper Canada, the 1791 constitution was suspended at this time, causing the colony's bicameral parliament to be dissolved. To replace these bodies and assist in governing Lower Canada, Colborne established a 24-member Special Council.
Colborne stepped aside as acting Governor General until the arrival of Gosford's formal successor, Lord Durham, on 27 May 1838. Colborne was promoted to the substantive rank of lieutenant-general on 28 June 1838. Durham remained in Canada only for a few months, resigning on 9 October and leaving for London on the fifth-rate HMS Inconstant on 1 November, after he learned that his policy of leniency towards the leaders of the prior year’s rebellion had been repudiated by the British Government. Durham's departure caused Colborne to again become acting Governor General. Colborne put down a second revolt in November and was confirmed as Governor General of British North America on 14 December. He left Canada in October 1839 after the arrival of his successor, Charles Poulett Thomson (who shortly thereafter  would be elevated to the peerage as Lord Sydenham). After arriving back in England, Colborne was himself elevated to the peerage as Baron Seaton, of Seaton in the County of Devon, on 5 December 1839.
In recognition of the "important services" rendered by Colborne, and following a message from Queen Victoria, Parliament settled an annuity of £2,000 on him and the next two heirs male who would succeed to the title.
John Colborne, 1st Baron Seaton