The pilot project, the first of it kind in any Scottish town centre, has attracted 2000 registered users in just four months.
And the link has been so successful that work is already under way to extend it beyond the town centre and will be complete by the end of February.
The project is spearheaded by Town Centre Activities (TCA) Ltd.
Managing director Emma Walker said: "We are very pleased at the take-up of the pilot project in Motherwell Town Centre.
"Businesses especially are delighted with the free service.
"We are now moving ahead with plans to introduce a similar service across five of the remaining town centres.
"All being well we would hope works on Coatbridge, Airdrie, Wishaw, Bellshill and Kilsyth will begin before the start of the new financial year in April.
"Since the service began last October there have been more than 10,000 log-ins, with many repeat visits. The average length of visit is 30 minutes.
"We are so pleased with the usage that the network is currently being extended up Windmillhill Street to the Civic Centre."
The WiFi project is being funded jointly by North Lanarkshire Council and TCA.
Overall the project is expected to cost around £140,000 over three years to include all the town centres.
Councillor David Fagan, convener of Regeneration and Infrastructure, added: "No-one in Scotland has introduced a free WiFi service on this scale, even among the cities.
"There were risks involved in the pilot, but it has been very well received and the number of users shows how popular it is.
"The aim is to help revitalise our town centres, support local businesses, improve footfall and encourage shoppers and visitors to spend more time in the town centres."
The system will require users to log-in to the network, which has filters in place to block unacceptable content.