Construction will begin at the bottom of Kenyon Street and make its way up through the North Tipp town and out the Dublin road over the next 12 months.
The 17 million euro project, which involves bringing natural gas to Nenagh, also includes work on the water and waste-water pipes on the streets.
Significant traffic restrictions will be in place for the duration of the project, diversions are in place and will be signposted.
Nenagh Independent Councillor Hughie McGrath insists the town is still open for business.
