It won’t replace the national NHS app.
The new service aims to support efforts to stop the spread of coronavirus.
The County Council and Oxfordshire’s five district councils will work to contact people that the NHS test and trace national system is unable to reach.
If local call handlers can’t get through either then trained staff from the City and district councils will visit cases at home and deliver letters explaining why they’re trying to get in touch and asking people to contact the call centre.
Oxfordshire County Council Public Health Consultant Adam Briggs said: "Our local contact tracing system provides another layer of support to help control COVID-19 in Oxfordshire
"If you are contacted, it will be a locally based person on the other end of the phone. They will talk to you about what you need to do to protect your friends and family whilst isolating, and about what support is available nearby.
"The overall aim is simple - to limit the transmission of COVID-19. By isolating when you have symptoms, getting a test, and picking up the phone when we call, we will give ourselves an even better chance to #stopthespread."
In a statement, Oxford Green Councillor Dick Wolff said he welcomed the decision, but thinks data quality needs to be improved: "From the outset, contract tracing lacked the local on-the-ground support that is so essential to achieving a high contact rate. This joint initiative by Oxfordshire's Councils is therefore very welcome. But, importantly, efforts now need to go into improving data quality and availability. Without this the best contact tracing system will fail to find those at risk of infection. What this means is that premises have to be responsible and display QR and residents have to be diligent about checking-in."
The service will run seven days a week and text messages will also be sent to people with mobile phones telling them to expect a call.