Salisbury Cathedral Spire was lit up green on Saturday to celebrate the award.
The Eco Diocese award is part of the wider Eco Church scheme, which is a nationally developed web-based survey and award scheme run by A Rocha UK.
The Award looks at a Diocese or Parish’s green ‘credentials’ in five areas: Worship and Teaching; Buildings; Land; Community Engagement and Lifestyle.
To achieve an Eco Diocese Bronze Award, 10% of the Diocese’s 500 local worshipping communities, which are spread across Dorset and Wiltshire, engaged with Eco Church, and 5% obtained an Eco Church Award.
In addition, the whole Diocese met Eco Church Bronze Award standards for its management of buildings and land. There was also a requirement for ethical investment of diocesan funds and for the inclusion of care for creation in training for ministry.
Andy Atkins, CEO of A Rocha UK the Christian based environmental charity which runs the award scheme said: “Salisbury is the first diocese to be awarded Eco Diocese status and it's our very great pleasure to do so.
"When we launched Eco Church in 2016 we had high hopes and expectations. To have reached this far so quickly is humbling, exciting and such a huge encouragement that so many churches in a diocese are working together to care for God's earth should be an encouragement to us all".
The Bishop of Salisbury, Nicholas Holtam, also the Church of England's lead bishop for the environment, said: “I am delighted and very encouraged that the Diocese of Salisbury is the first to win this award. As the lead bishop on the environment for the Church of England I am delighted my own diocese is first and I also hope that others will be close behind us,
"The recent IPCC report on climate change and the WWF report on the destruction of biodiversity means the care of God’s earth is urgent. I hope that becoming an Eco Diocese will encourage us to do more and better. ”
"Our target to become an Eco Diocese was to have 50 churches registered and now we have 70 and we have Bronze, Silver and Gold awards. And we have more churches still working towards getting their own award.
"It shows that as a Diocese we recognise that the care for God’s creation is at the heart of ministry and mission”.
David Morgan, Chair of the Salisbury Diocesan Environmental Group said: “It is exciting and encouraging to see caring for creation come up the agenda of many parishes in the diocese. Some of our churches have been on this journey for many years; for others, it is a new understanding of our responsibilities which they have embraced and acted upon.
"All have engaged with the biblical mandate to be stewards of God’s creation and with practical issues that our common home faces (such as climate change, plastic pollution, loss of wildlife.
"This proves that even with a listed church building, it is very possible to achieve an award. Bronze Eco Diocese achieved but now onto Silver!”
"As well as their 25 churches gaining awards, (19 Bronze, 5 Silver, and 1 Gold), the Diocesan offices in Salisbury also picked up a Bronze award.
Announcing the award, Colin Brady, Social Justice Programme Manager for the Diocese of Salisbury said: “Last week we received news of two more churches gaining their Bronze Eco Church award, and notification that our offices in Salisbury had met the criteria for its own Bronze award, and suddenly we were there. And we are confident that more local awards will follow
"The bug and insect life of Dorset and Wiltshire has never had it so good.
"Many of our congregations have had lots of fun building bug hotels in their churchyards, adding a few more points towards their Eco Church awards with a clear message that Christians care for Creation.”
Helen Stephens, Church Relations Manager for A Rocha UK said: This is a huge 'win' - for churches, for the individuals who work so hard within them, for their communities and for God's earth.
"Whilst the honour of first Eco Diocese goes to Salisbury, others are very close to becoming Eco Dioceses.
"Parishes that had been involved in Living Churchyard and other ecological projects were encouraged to look at the new scheme, and many held special events working on ways of being more environmentally friendly.”