Also, the local authority has renamed the path previously known as, the Emerald Way cycle route, it will now been known as the Platinum Way.
Bucks Council says the name was chosen as a nod to the upcoming Platinum Jubilee.
Funded by the Department for Transport the local authority has widened footways, added cycleway crossing points, and constructed new signage.
The 5km cycle route runs from Aylesbury Vale Parkway along Rabans Lane and through Fairford Leys into the town centre.
After the phase one improvements, part of the Platinum Way route now passes through Somerville Park.
Bucks Council reports that several community events have coincided with the pathway improvements.
Chiltern Rangers and volunteers have planted along the route.
Nature-themed art sessions have also been held by the path including painting and making and decorating bird boxes.
Bucks Council has announced that further designs will be completed for three new cycle and pedestrian crossings in Rabans Lane, Fowler Road, and Fowler Road near Bracken Way, in the coming months.
Later in the year, during National Tree week (26 November to 4 December), 1,000 bulbs and hundreds of trees will be planted as a native hedgerow to make Somerville Way and Haydon Hill better for wildlife. Local schools and community groups will be invited to help with this planting, Bucks Council says.
Bucks Council chairman Dev Dhillon cut the ribbon to mark the completion of the first phase.
He was officially opening a new section which runs next to Prebendal Farm Community Centre.
Council officials also checked out some of the community artwork which has been done as part of the project.
Chairman Dev Dhillon said: “We are committed to investing in our local green infrastructure, making it both easier and more enjoyable for more people to walk and cycle.
"Not only are there huge personal benefits for our health, but there are also huge benefits for the environment – because less journeys by car help to reduce traffic congestion and improve air quality.”
More information is available on the council website here.