The minor injuries unit at Tenby Cottage Hospital was closed as part of a shake-up of health services back in 2013 leading to public demonstrations.
Hywel Dda University Health Board hopes the new nurse-led walk-in service will open in July.
The board said the unit would provide "convenient access" for residents.
St John Ambulance Service will provide treatment for minor injuries over the Easter period.
Plans to open a new minor injuries unit in Pembrokeshire have got a step closer - four years after protests against the closure of the previous one.