In a televised inaugural speech Thursday, Phuc vowed to push up with reforms, fight corruption and defend the country's sovereignty.
The appointment of Phuc, who rose from governor of the central province of Quang Nam to deputy prime minister five years ago, was a mere formality after he was picked at the Communist Party's congress in January as the sole candidate to replace Nguyen Tan Dung, who was removed from office Wednesday.
Analysts say Phuc is likely to continue with economic reforms and international integration.
PM leaves for Vietnam, Cambodia