The land and buildings, covering 3.3 acres, which had been on the market since December 2018, have been bought by Pembrokeshire-based housing association ateb.
The organization, whose collective purpose is to create better living solutions for communities in west Wales, will seek planning permission to develop the site.
Potential uses include office space, collaborative community spaces, a community café, and a residential development to meet the housing needs of the local area.
Ateb is also intending to relocate its headquarters from its existing premises at St Thomas Green, Haverfordwest.
Ateb chief executive Nick Hampshire said it was important to the organization that its headquarters remained in Pembrokeshire’s county town.
“We are delighted and proud to become the new custodian of the old Library site and look forward to evolving this exciting regeneration project,” he said.
“The new homes, subject to planning, are very much needed for the local area.”
Mr Hampshire reassured residents with parking concerns that ateb would engage with those affected to find the best solution going forward.
“We are aware of the issues around parking and look forward to engaging with residents and local councilors to consider their concerns and objections,” he added.
In the meantime, the car park will remain open and will be run in the short term by Pembrokeshire County Council.
It has been a long and protracted process to get the old library into development with the site having been up for sale since 2020.
In July last year PCC stunned residents by advising them to seek legal advice if they had concerns about parking availability.
In November county councilors sat down and listened to resident’s fears about the future of Haverfordwest without effective development in the top end of High Street.
Pembrokeshire County Council says ateb’s plans will create local employment and re-using the empty town center building will generate new footfall in the upper end of High Street.
PCC also say the development of much-needed town center residential accommodation is important, all designed in a style in harmony with the importance of the location.
Ateb intends to carry out the development in phases, with the timescale for submitting the application for planning consent set for later in the year.
The planning stage is likely to take at least 12 months with ateb setting a goal to start working on the project in 2023.