The clock, stored in a Buddhist temple, was submerged by the tsunami on Japan's north-eastern coast that followed the devastating earthquake, which killed more than 18,000 people in March 2011.
Its owner, Bunshun Sakano, then tried to fix the clock, without success.
But when a smaller quake hit 10 years later, he says it began working again.
According to the Mainichi Shimbun newspaper, the spring-driven clock was stored in the Fumonji Temple in Yamamoto, in Japan's Miyagi region. Miyagi and neighbouring Fukushima were badly hit by the 2011 earthquake and tsunami.
On 11 March 2011, the temple, which stands a few hundred metres from the coast, was struck by the tsunami's waves, with only its pillars and roof spared by the deluge.
After the disaster, Mr Sakano, the temple's head priest, rescued the clock from the debris. He rewound it, but could not get it to start.
Then on 13 February this year - weeks from the anniversary of the disaster - the same region was struck by another powerful earthquake. Meteorologists said they believed it was an aftershock of the massive 2011 quake.
The following morning Mr Sakano, while checking the main hall for any damage, heard a ticking sound and found the clock was moving again. Two months later, it is still working.
The 80-centimetre (31-inch) clock, which Mr Sakano bought in an antique shop in nearby Fukushima several years before the 2011 disaster, seems to have been shaken back into action by the force of February's earthquake.
A representative of Seiko, the clock's manufacturer, told the Mainichi newspaper: "It's possible that the pendulum, which had stopped, started moving again with the shaking of the earthquake, or that dust that had built up inside came loose."
Mr Sakano, whose temple served as a base for volunteers after the earthquake, says he has taken inspiration from the clock restarting.
"Maybe it's pushing me to move forward with new determination," the 58-year-old said. "It's like a sign of encouragement that the real restoration is to come."