In England the ban will last until at least 21 February, and be kept under review, while in Wales it will run until 31 March.
In exceptional cases in England, such as where tenants display anti-social behaviour, possessions can go ahead, the ministry of housing, communities and local government said.
The eviction ban had been set to expire this weekend.
Landlords in England will still be required to give six-month notice periods to tenants until at least 31 March – again with the exception of the most serious circumstances.
The courts will continue to prioritise cases, such as those involving anti-social behvaviour or illegal occupation.
The measures will be kept under review, the government added.
It comes after Citizens Advice estimated half a million renters are currently in arrears with the pandemic fuelling economic hardship.
Agent trade body Propertymark criticised the last-minute nature of the extension to the ban.
Chief policy advisor for Propertymark Mark Hayward said: “In light of the recent lockdown, it is no surprise the UK Government has made today’s announcement, yet over the past few weeks the UK government has held off updates about evictions to the sector making it impossible for agents to respond and plan for the difficult winter months ahead.
“The whole of the private rented sector has been impacted as a result of Covid-19 but we must recognise that the courts already faced a backlog of cases prior to the pandemic.
“Although the new mediation pilot will help, it is important to take steps back towards normality so that both landlords and tenants have access to the justice system, while putting measures in place to offer further support to tenants who have built up Covid-related arrears through no fault of their own.”
At the same time, the government has provided an extra £10m and asked all councils in England to help accommodate rough sleepers and make sure they are registered with a GP.
Communities secretary Robert Jenrick said: “At the start of this pandemic we made sure that the most vulnerable in society were protected.
“This winter, we are continuing in this vein and redoubling our efforts to help those most in need.”
Polly Neate, chief executive of housing charity Shelter, added: “You cannot follow the order to stay at home if you don’t have one – making the government’s decision to stop bailiffs from physically evicting people this winter the right call.
“While this ban doesn’t halt the evictions process entirely, it is the minimum required to keep more people safe in their homes.
“Even with the bailiff ban extended until February, we know people will still become homeless. The government’s extra £10m for rough sleeping support and to make sure people are registered with a GP is very welcome and essential.”
Welsh housing and local government minister Julie James said: “We are taking further action to protect public health and support Welsh tenants.
“This is an extremely difficult time for many people and renters should not be forced out of their homes, at a time when we are asking people to stay at home and when they will have less access to advice, support and alternative accommodation.”