TNT Post did not disclose the cost of the deal, but a spokesman said it would invest several million pounds over the next few years to improve and expand the network. It will also use the network for non-parcel deliveries.
TNT Post had previously used Express Dairies' residential delivery service through milkmen until the latter's losses forced it to scrap the service in November last year.
The JD Williams network carries around 12m parcels and packets a year sent by businesses and consumers. It has 194 employees, supported by a network of more than 2,200 self-employed couriers.
Nick Wells, chief executive of TNT Post UK, said: "This network acquisition is a big development for the TNT Post business that really propels us forward in terms of business growth and our position in the UK postal market.
"We will be taking on the entire courier network including all employees and the self-employed couriers will be able to continue to offer their services and will be encouraged to do so."
Following the complete opening of the UK postal market TNT Post is now processing more than 60m letters a month and its client list includes Sky, Barclays, Lloyds TSB, Npower, Thames Water and Ikea.
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