Users across the UK complained of intermittent service on Monday evening, with apparent connectivity dropouts every so often.
Though more people are at home during lockdown, relying on broadband services for home working and entertainment, Virgin Media said the issue was not a result of increased usage or a lack of capacity.
A spokesman said it had been fixed in the early hours of Tuesday morning.
"We know how frustrating this was for customers and we sincerely apologise for any inconvenience caused," he said.
While some customers said their service was running as normal on Tuesday, others claimed they were still experiencing problems.
One user said on Twitter: "I still have an issue - no internet at all for any of our users in the house."
Another wrote: "Virgin Media is still playing up? Good thing I don't need to use the Internet extensively for work... OH WAIT."
Reports of connection problems on the downdetector website were also being posted, though the volume had decreased since Monday evening.
The cause of the intermittent outage was not clear.
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