The acquisition is the latest in a string of purchases by SpiriTel, which sees itself as an active consolidator in the highly-competitive UC market and has bought 11 businesses since 2005.
It said today it hoped to start cross-selling mobile voice and data solutions into Nessco's customer base.
Nessco specialises in healthcare, local government and hospitality customers across Scotland.
It made sales of £3.2m and a pre-tax loss of £50,000 in the 12 months to 31 March 2009, but made a small pre-tax profit in the nine months to the end of December.
SpiriTel plans to integrate Nessco into its Business Division, which currently has offices in Cardiff, London and Wigan.
"[Its] operations are particularly complementary to SpiriTel's, and we are confident of a swift and effective integration," said SpiriTel chief executive Alastair Mills. "We are delighted to complete our first acquisition in Scotland, a deal of strategic importance to the group which will enable us to offer genuine nationwide engineering coverage to our growing base of customers."