Brains is putting nine of its Vale of Glamorgan pubs up for sale.
The Cardiff brewery is seeking an asking price of £87.3 million for nearly a hundred Welsh pubs, as it seeks to combat financial pressures caused by COVID.
Last year, Marston's stepped in to run 156 Brains' pubs on a long-term lease, in a move aimed at safeguarding around 1300 jobs nationwide.
The two-week firebreak lockdown last Autumn is said to have cost the brewery around £1.6 million.
Most of the properties on the market are freehold and property advisors are expecting ''significant levels of demand''.
SA Brain & Co chief executive Jon Bridge, said the last 18 months had ''clearly been a challenging period'' for the firm.
He added: ''However, through the steps taken and support we have received from our stakeholders, we continue to brew our famous beers in the heart of Cardiff.''
''There has been a significant amount of interest in the portfolio of pubs and this strategically planned sale is the next step on the positive journey of recovery for Brains.''
Locally, the Brains pubs put up for sale in the county include:
Around 34 pubs in and around Cardiff are also included in the deal, including Coopers Carvery at Culverhouse Cross, The Packet in Cardiff Bay, and The City Arms in the city centre.
The pub chain is said to earn Marston's around £5.4 million a year.
Estate advisors Avison Young are overseeing the sale and are aiming to offload the entire portfolio to a single investor.
Peter Constantine, managing director of Avison Young's leisure team, said: ''This is a rare opportunity to acquire a large, high-quality package of public houses located in strong trading positions across Wales.''
''They benefit from a secure income stream let to an excellent covenant. We anticipate significant levels of demand as packages of this quality rarely come to the market.''
Two years ago, Brains moved to its current brewery in the East Moors area of Cardiff, after vacating its former home, now earmarked for the Central Quay development.