Elgizar Sabirov, who headed the Senate's defense committee, replaces Murat Sharifkhodjev.
Addressing the Senate, Uzbek President Islam Karimov praised Sharifkhodjev's work, but said ill-health was preventing him from continuing.
The Senate is due today to discuss ratification of a union treaty with Russia and approval of resolutions on Uzbekistan joining the Eurasian Economic Community.
RFE/RL Central Asia Report
SUBSCRIBE For regular news and analysis on all five Central Asian countries by e-mail, subscribe to "RFE/RL Central Asia Report."