The 12th Parliament of Upper Canada was opened 15 January 1835. Elections in Upper Canada had been held in October 1834. All sessions were held at York, Upper Canada. This parliament was dissolved 28 May 1836 by the new Lieutenant Governor, Sir Francis Bond Head. Head ordered a new election because the House of Assembly, dominated by reformers, had refused to pass any new money bills. The assembly also labelled Head a deceitful tyrant after he had invoked his right to consult them (the representatives of the people) only on certain specific matters. It was succeeded by the 13th Parliament of Upper Canada in November 1836.
The House of Assembly of the 12th Parliament of Upper Canada had two sessions 4 February 1817 to 7 March 1820:
Both the House and Parliament sat at the third Parliament Buildings of Upper Canada.