The areas - which have been named after streets they include - are Barrington (in Huntington), McNicol (in Fairfield), Ngaere (in Chartwell), Willoughby (in Whitiora), Lethborg (in Dinsdale), Heath (in St Andrews), Howell (in Hillcrest) and Tamihana (in Fairfield).
A safer speed area is defined as a set of streets where the danger to people is deemed too high if vehicles travel at the existing 50km/h speed limit.
Most of the areas back on to schools and serve a range of purposes as well as a transport function, including where people might be exercising, walking dogs or going to the shops.
A resident in the Tamihana area, Peta Goldsworthy, said the reduced speed limit had to be enforced or it wouldn't work.
"Hamilton City Council has been very good about installing traffic-calming measures in recent months but these have not stopped hoons or motorists using our streets as a rat-run.
"I would hope we would see some enforcement alongside the introduction of the new speed limit to make the area safer, particularly for neighbourhood children."
The decision followed recent consultation with the community and key stakeholders, including the Automobile Association, the Road Transport Association and Waikato Regional Council, which included the distribution of more than 1000 leaflets and an awareness campaign.
Only 20 submissions were received, half in support and half opposed.
The council's strategy and policy committee chairwoman, councillor Maria Westphal, said that she was pleased to see the project approved.
"Reducing speed limits by just 10km/h on our local streets will bring significant road safety benefits to all road users, particularly children on their way to school, cyclists and walkers."
Ms Westphal said slowing the traffic in residential streets was intended to re-claim the streets for their residents.
"The difference between knocking someone over at 40km/h and 50km/h is a life."
The council worked with the NZ Transport Agency and police to pull the project together and received funding from the Road Safety Trust.
The speed reduction starts on October 17 and signs and road markings would show where the eight areas are.
ON THE WEB
www.saferspeedarea.org.nz