Britons visiting the tourist island, also known as Zante, were forced to evacuate their hotels, with half-dressed parents waiting by the pool for hours in the cold clutching children in blankets at around 2am local time (1am BST).
One said they had "never moved so quickly" when the "screams and alarms" began on Friday morning.
Three people were taken to hospital, two slightly injured, authorities said.
Local media reported a 15th-century monastery had been damaged, as well as items thrown off shelves in houses and cracked paving slabs.
Laura Sallabanks from Lincolnshire was staying at a resort in Alykes on the island.
She told Sky News it "felt like the whole building was swaying around us" when the quake hit.
She ran to the next room to grab her nine-year-old daughter, following guests rushing to get outside.
They sat with locals for several hours, who brought raki to help calm their nerves - a traditional aniseed flavoured alcoholic drink.
Even the next morning, Ms Sallabanks said she could feel "dull rumbles" of aftershocks.
Kaytee Baylis, from Rugby in Warwickshire, was woken when the power cut out.
The light from her phone stopping charging illuminated the sight of her bedroom mirror "shaking vigorously".
She looked over and saw her son in the next bed "shaking" and grabbed him in a panic.
When the tremors subsided, they returned to their hotel room in Kalamak - but aftershocks kept them awake all night.
Ms Baylis told Sky News she was "still a bit shaky this morning" but is focusing on "hoping the rest of our holiday goes smoothly".
Chanelle Ford, who is 24 weeks pregnant and visiting from East Sussex with her partner Shane, also told Sky News she looked into booking an early flight home.
There were "very few" options available, she said, so the pair plan to stay put until their original flight on Sunday.
Another tourist, Joanna Jones, from Liverpool, compared the to "Jumanji", the adventure movie series.
"The floor, beds and every bit of furniture bouncing and shaking up and down.
"I had to spread my feet wide apart and stretch my arms out either side to keep balanced. It was petrifying."
The tremor was felt in Athens, the Greek capital, and as far away as Albania, Italy, Libya and Malta.