"After friendly consultations between China and the US, the transfer of the underwater drone was smoothly completed," CNN cited a Chinese Defence Ministry statement as saying.
According to the Pentagon, the US would continue to investigate the events surrounding the incident.
China had seized the US drone from the disputed South China Sea waters. President-elect Donald Trump had slammed China for seizing the drone. Trump had tweeted: "China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unpresidented (unprecedented) act."
Meanwhile, China on Monday denied that it had stolen the drone and said that the device was picked up from causing any obstruction to the freedom of navigation in the South China Sea.