They will assess incidents where Wakefield officers have been called out to incidents where people may be suffering with mental ill-health and give advice to officers.
The nurses will also help find support for people who frequently have contact with the police because of mental health problems.
West Yorkshire Police have teamed up with NHS Wakefield Clinical Commissioning Group (CCG) to launch the “street triage” initiative.
It has already been tried out in other parts of West Yorkshire and is coming to Wakefield after a successful bid for funding.
Ch Insp Kate Riley said: “The new scheme means officers will be able to provide a more appropriate response to people who present with mental health issues.
“The street triage scheme is a great example of where we can work with our partner agencies to provide the right service to all sections of society, especially vulnerable people.”
The law allows police to detain people with mental health problems to make sure they are safe.
But research has found that detention is not appropriate for most people.
Ch Supt Mabs Hussain said: “A cell in a police station is clearly not the right place for a person who is experiencing mental health issues, and it is only ever used as a last resort as a place of safety. This scheme will hopefully reduce the use of police cells in this way.”
Dr Clive Harries, Wakefield CCG’s mental health lead, added: “The mental health nurses will be able to offer the appropriate support whilst an incident may be happening, ensuring the person potentially suffering from mental ill health gets the support they need.”