The takeover will see General Logistics Systems (GLS) expand its presence across the country, particularly in the west of Canada, and allow the company to unlock "significant growth opportunities".
News of the expansion came as Royal Mail announced details of its annual festive recruitment drive which will see thousands of seasonal workers taken on to help existing staff.
Royal Mail has been in Canada since 2018 and operates two hubs with 27 depots and some 1,400 workers.
A deal to buy Mid-Nite Sun Transportation, which operates as Rosenau Transport, will see it expand and create a new link with GLS's current operations on the west coast of the US.
It will be funded with existing cash and borrowing and see GLS take on 24 facilities in four provinces, once the deal is completed by the end of the year.
Martin Seidenberg, chief executive of GLS, said: "The addition of Rosenau Transport to GLS complements and enhances our ‘accelerate’ strategy.
“With its strong presence in Western Canada, high quality, entrepreneurial culture, as well as freight capabilities and parcel potential, Rosenau Transport's model is similar to our existing Canadian business and provides an excellent fit.”
Rick Barnes, president of GLS Canada, said: "As we link two regional carrier networks together, with direct service to most cities and towns in the country, we will produce one of the most integrated transportation systems in Canada.
“The extended geographical reach will provide our 30,000 clients with a new, national and international alternative for all of their shipping needs.”
Ken Rosenau, president of Rosenau Transport, added: "Rosenau Transport is excited to join the GLS family and align with an industry leading organisation that will open new opportunities and markets on a global scale.
“The combined networks of GLS and Rosenau Transport will allow us to offer a comprehensive Canadian solution to better serve our clients.”
Meanwhile, Royal Mail launched a drive to recruit around 20,000 seasonal workers to help with the Christmas post and increasing amounts of online shopping.
Temporary jobs will be available from the end of October to early in the new year, with Parcelforce also looking for seasonal drivers and other workers.
Around 17,150 seasonal workers are needed in mail centres, distribution hubs and data centres across England, with 1,800 in Scotland, 650 in Wales and 500 in Northern Ireland.
The seasonal workers will help sort Christmas parcels and cards as well as the growing amount of online shopping orders.
An additional 3,650 workers will be recruited on Royal Mail Group's express parcels business, Parcelforce Worldwide, 1,500 at its international parcel hub at Heathrow and 650 data inputting roles at three sites in the UK
Royal Mail chief people officer Zareena Brown said: "Our seasonal workforce is incredibly important to our operation and we very much look forward to welcoming those who return year after year as well as those who may be joining us for the first time.”