Tymoshenko will serve as acting prime minister until Ukraine's parliament convenes to vote on her nomination. The position had been vacant since Viktor Yanukovych resigned from office in December.
Yushchenko meanwhile appointed Oleksander Zinchenko state secretary today within a new structure created inside the presidential administration.
Petro Poroshenko was named secretary of national security and defense.
Yushchenko issued the decree on the appointments just before traveling to Moscow on his first official state visit as Ukraine's president.
"I would like to emphasize that this is my first trip outside Ukraine," Yushchenko said. "This is a sign of high respect given to our relations. I would like to say that we always have and always will view Russia as our strategic partner."
He met with Russian President Vladimir Putin, who expressed hope of continuing close cooperation with Ukraine.
Putin said after the meeting that Yushchenko's trip to Russia was a good sign.
"We're glad that the difficult period of political processes ended in Ukraine," Putin said. "We're glad that the situation is stabilizing and that there is a government now. We hope that our relations with Ukraine will develop progressively, as they have until now."
Putin had openly backed Yushchenko's opponent, Yanukovych, in the presidential election that culminated in the repeat runoff in December.
(Ukrainian Service/Reuters)[For a full archive of RFE/RL news and analysis on the recent political crisis in Ukraine, see our dedicated Ukraine's Disputed Election webpage.]