Tymoshenko is serving a seven-year prison sentence after a conviction on charges she abused her power when she helped broker a natural gas deal with Russia's Gazprom when she was prime minister in 2009.
"The conviction orchestrated by the current administration was conducted under recycled Soviet-era codes and is a poorly veiled effort to dispose of a political rival," said Inhofe in a statement.
The measure calls on the U.S. State Department and the Organization for Security and Cooperation in Europe to apply diplomatic pressure on Ukrainian President Viktor Yanukovych to secure Tymoshenko's release.
Former Interior Minister Yuriy Lutsenko, a Tymoshenko ally, is serving a four-year prison on embezzlement charges.
Tymoshenko's attorneys said they'd take the case to European courts. The European Union said trials for opposition leaders in Ukraine didn't meet international standards for "fair, transparent and independent legal processes."
Ukraine has parliamentary elections in October. Tymoshenko lost her bid for the presidency in a bitter campaign against Yanukovych during the country's last election cycle.