Obama in January rejected a permit filed by TransCanada to build the Keystone XL pipeline because authorities in Nebraska hadn't settled on a final route.
Fallin, a Republican, told an energy exhibition in Canada that Obama was out of step on the issue.
"The president doesn't understand the magnitude of the energy sector and how it can generate strength in the economy," she was quoted by the Calgary Herald as saying.
Supporters say the pipeline is good for the economy and energy security. Critics counter that it represents a move from green energy trends and creates environmental concerns.
TransCanada Corp. in May submitted a new application to the U.S. State Department for the Keystone XL pipeline from the Montana border with Canada to Steele City, Neb. It needs federal approval for that section because the overall project would cross international borders.
The U.S. section of the pipeline to service southern U.S. refineries was approved by the Obama administration this year.
TransCanada said that, if approved, construction for Keystone XL would begin in early 2013. The pipeline won't pass through Oklahoma.