GT Law has opened a new 12,000 sq ft premises at Knowsley Industrial Park.
The law firm, which is moving a team from a smaller office in the borough, has signed a five year lease with Dams International, which is expected to create 100 new jobs.
Gordon Tucker, GT Law director, said: "After launching a fairly small operation down south last year we are now growing into one of the leading law firms in the UK, specialising in accident compensation and personal injury claims.
"Our success in such a short period of time meant we had to move somewhere quickly which had both quality commercial space available at a good price and a quality workforce.
"The move to Kirkby is providing us with both and that's why we signed a five year deal as we are confident that the business will continue to grow.
"Our market is hugely competitive but our high level of service and the levels of compensation we are achieving means our reputation is growing across the UK.
The company works on a no win no fee basis and takes on cases where the three year limitation period for making a claim is fast approaching. It launched in Essex last year.
Knowsley Industrial Park covers 1,000 acres. Both the tenant and landlord represented themselves and the rental agreement was not disclosed.