The public counter will now be open from 8am to 4pm, rather than closing at noon.
Police Minister Liza Harvey visited the station on Thursday to announce the new opening hours, which came into effect on Monday.
She said the station was significant to the Hills community and the extended hours would increase the level of service.
Swan Hills MP Frank Alban welcomed the news.
‘I would also like to acknowledge the efforts of Sergeant Browne, Officer in Charge of Mundaring Police Station, who has been working with the community, local government, and the East Metropolitan District Office since 2012 to address community concerns,’ he said.
The Mundaring Chamber of Commerce, several Shire of Mundaring councillors and Hovea Residents and Ratepayers Association also backed the plan.