A 35 year-old Noongar man has died in custody in Perth.

WA Police said the man was arrested about 2pm on Thursday by Midland Police officers for allegedly breaching bail conditions.

He was subsequently taken to the Perth Watch House where he was assessed by a nurse on admittance.

Police say that around 8pm, a change in his behaviour was noticed and following consultation with nursing staff, "a decision was made to convey the man to Royal Perth Hospital for further assessment".

A police spokesperson said "tragically he suffered a medical episode while still in police presence prior to being admitted".

"Despite the best efforts of Emergency Department staff, the man could not be revived," they said.

The death is not being treated as suspicious and a report will be prepared for the Coroner.

More than 600 Indigenous people have died in custody since the Royal Commission into Aboriginal Deaths in Custody brought down its findings and made over 300 recommendations in 1991.

Noongar advocate Megan Krakouer, who is in contact with the man's family, told National Indigenous Times the death is "heartbreaking".

"People with particular needs must be availed to a secure facility with seasoned health professionals, and health screening resources, and this should not be rocket science," she said.

"Police watch houses are not such a place for affected individuals. Governments need to start funding specialised facilities, where people can be treated for AOD addictions or withdrawals, drug induced psychosis, or to sober up.

"Love, respect and sincerest condolences is extended to all the family."