The new secure cabinet is available for use at all times by dialling 999 and quoting the code on the door, located near the entrance of Christchurch Baptist Church in Bargates.
The lifesaving machine costs £2,400, which covers a four year contract.
It was funded through donations from the church and the wider community as well as councillor's ward budgets.
Julian Sheppard, of Christchurch Baptist Church, said: "We are very grateful to Cllr Peter Hall and Cllr Wendy Grace who very generously donated £400 of their town centre ward budgets towards the defibrillator.
"The Minister Rev Chris Brockway affirmed a need in the community and the church accepted this commitment.
"The church is thrilled to be helping the community with this resource which might help save the life of at least one of the 140,000 people in the UK who experience sudden cardiac arrest each year."
The defibrillator was officially launched last month by Christchurch MP Christopher Chope alongside the mayor and mayoress of the town Cllr Nick Geary and Mrs Gillian Geary.
It is now available for members of the public to use.
Automated external defibrillators (AED’s) are purposely easy to use. Anyone can use them – the machines talk you though what to do, and that, alongside advice from emergency call-handlers, means that anyone can help save a life.
Cardiac arrest does not discriminate against age, sex or fitness – it can happen to anyone, anywhere and at anytime. It can be caused by many things including heart attacks, strokes and major trauma, and early defibrillation for patients in cardiac arrest can make all the difference to the outcome.
Some local businesses in Bargates and members of the congregation have already attended a free training course at the church. Another session is set to take place at 7pm on Monday, September 4.