Liverpool City Region metro mayor Steve Rotheram said that regional leaders had reached an agreement with the Government after residents pushed for the change.
Fitness facilities have been closed in the Liverpool City Region since the area entered the "very high risk" category on October 14.
Watch: Which areas are in what tier in the UK?
However, they were allowed to remain open in Lancashire even when it joined the top tier.
The disparity sparked outrage in the region, as more than 350,000 people signed a petition titled 'Prevent gyms closing due to a spike in Covid 19 cases'.
On Wednesday morning, Mr Rotherham told BBC Radio Merseyside that ministers eventually agreed to bring the region "in line" with other Tier 3 areas.
Reading a statement on behalf of local leaders, he said: “Collectively, we have consistently requested the scientific evidence that supported the imposition of the suite of measures under Tier 3 and we pointed out the inconsistency of the approach following the announcement that Lancashire would not in fact have exactly the same package of restrictions as our city region.
“Talks continued until late last night and the Government have agreed with the case I put forward on behalf of city region leaders and that they would now bring us in line with other Tier 3 areas.
“This would mean soft play areas would be closed but gyms could reopen.”
The announcement comes after MPs probed Health Secretary Matt Hancock on the issue.
Speaking in the House of Commons on Tuesday, the Labour MP for Halton Derek Twigg said: “Given that Lancashire and now Manchester in Tier 3 will be able to keep their gyms open, can I simply ask the Secretary of State, will he either use the Government’s powers or give the powers to local council leaders in Halton and Merseyside to reopen gyms in that area?”
Mr Hancock replied: “Why don’t we have a conversation about it and see whether we can make any progress?”
The Health Secretary had already faced calls from Conservative backbenchers to allow the fitness facilities to reopen.
On Monday, Southport MP Damien Moore called on Mr Hancock to “get our gyms open”, describing them as “part of the solutions, not part of the problem”.
Mr Moore added: “The gyms in Lancashire are open, the gyms in Merseyside are closed. The deal that was struck for us wasn’t a good deal for my constituents in Southport.”
Watch: Could a necklace help you keep your distance?