Whistl chief executive Nick Wells was joined by newly elected MP Phil Boswell at the event.
The business has moved its existing Coatbridge operation five miles over to a 5,000sqm depot in Tannochside, Uddingston, which it said is three times the size of its former home.
Whistl has operated in Scotland over the past nine years and collects and sorts an average of 2 million items of mail a week before handing over to Royal Mail for delivery.
The company collects mail and packets from 250 individual collection points across Scotland, with 1,200 clients in the public and private sector including Aegon and Standard Life.
Its most remote Scottish customer is the Western Isles Council, which uses Whistl for its Hybrid Mail services.
The Tannochside depot employs 150 people in a range of jobs including operations and transport. It has also developed roles for young people through the firm’s apprenticeship scheme.
Wells said: “The tripling of our capacity in Scotland with Tannochside will allow Whistl to further expand our customer base and continue to provide a high-quality and cost-efficient service.
“We are delighted to be investing further in Scotland, enabling more businesses and the public sector to benefit from our cost-efficient postal solutions and dedicated account management.
“This investment demonstrates our commitment to and leading role within the UK postal market.”
Last month the main conditions of a management buyout of Whistl were provisionally agreed between its managers and owner PostNL, following a review of PostNL's UK activities.
Whistl, which has been a wholly owned subsidiary of PostNL since 2011, was previously called TNT Post UK prior to a rebrand in September 2014. It had been a subsidiary of TNT Group until 2011.
The company, the UK’s second largest postal operator, has around 1,500 employees and a turnover of £625m. Alongside Tannochside it has UK depots in Leeds, Warrington, Bristol, Iver, Rugby and Newtownabbey while its head office is in Marlow.
Whistl also recently revealed that it had secured a number of new contracts that would strengthen its letter collection and DSA division. The DSA business has over 56% market share in the UK, handling around 3.8 billion items of mail per year.
