Cosmopolitan Housing Association has completed 23 'extra-care' apartments on Cartmel Road in Huyton.
The rental flats will be run in partnership with Knowsley Council and Knowsley Primary Care Trust.
Bootle-based Lockwoods Construction started on site in August 2008 and completed the building in December 2009.
The first residents started to move in before Christmas and the purpose-built scheme is expected to be fully occupied by the end of January 2010.
Marston Gardens will offer both independence and day-to-day support both for older people and other adults with support needs, including people with learning difficulties. The homes are all for rent and residents will be nominated by Knowsley Council's Health and Wellbeing team.
Residents will benefit from their own self-contained one or two bed apartment, which include a kitchen, lounge and wet room with walk in shower. The complex also offers a communal lounge and kitchen, laundry room, assisted bathroom, IT suite, treatment and therapy rooms, sun lounge, gardens and car parking.
The scheme was developed by Cosmopolitan Housing Association with grant funding of £1.3m from the Homes and Communities Agency, with the balance jointly funded by Knowsley Council and Cosmopolitan.