The populist premier's win signals a further rightward shift in the traditionally conservative province, and comes despite a series of controversies and gaffes from Smith, 52, since she first became premier in October.
Her victory is expected to lead to more tension between Alberta and the federal Liberal government, which aims to cut climate-warming carbon emissions 40-45% by 2030. That would require significant emissions reductions in Alberta, Canada's highest-polluting province and home to country's oil and gas industry.
In 2014 she crossed the floor to join the Progressive Conservatives, a move that backfired when she failed to win the conservative nomination to run in the provincial election a year later. Alberta conservatives suffered a rare defeat in 2015, bringing the New Democratic Party's Rachel Notley into power.
Her UCP leadership campaign promised she would stand up to the federal government and proposed a controversial Alberta Sovereignty Act, which was watered down before becoming law on the grounds it was unconstitutional.