More than 100 people attended the opening and dedication of the refurbished base, which was followed by service awards.
The awards recognised a total of 163 years of service to the organisation in the Alexandra area.
Linda Stephen, of Alexandra, who had given more than 35 years' service, was awarded life membership.
St John Alexandra area chairwoman Pat Shanks said Mrs Stephen "embraces all the core values of St Johns".
She joined the organisation in 1977, starting as a first-aider on the sport grounds, and then joining the ambulance service.
She later ran first aid courses in schools and in the community and training sessions for members, before retiring from St John in 2010.
"Although she's retired, she's still involved today," Mrs Shanks said. Life memberships were "not given out lightly".
The organisation set up in Alexandra in 1936 and part of the current building was purchased in 1971, she said.
It had been expanded and refurbished several times since then.
The latest upgrade had been almost a decade in the planning.
Major grants were received for the project from the Central Lakes Trust, the Otago Community Trust, the Alexandra Lions Club and a bequest from Fiona Mason. Many other individuals and community organisations had also raised funds for the revamp.
The exterior of the building remains the same but the interior has been changed substantially, with an upgraded kitchen, changes to the duty office, crew room, bedrooms, reception and hall, training and study rooms, to make it more user-friendly.
"St John is not just buildings and ambulances, it's an organisation that is responding to community needs," St John South Island Region Trust Board chairman Geoff Ridley, of Christchurch, said at the function.
It was active in youth development, nurturing young people, who would continue its service to the wider community.
St John faced challenging times with its funding from the Government capped for four years, while demand for the ambulance service was growing by 5% a year,Mr Ridley said.
