60 of the new vehicles will be added to the DIY giant's delivery fleet in a bid to reduce road miles.
The addition of 60 double-decker lorries will save B&Q's delivery fleet around 4,800 road miles and 4,600kg of carbon dioxide emissions every day.
The new vehicles will be introduced to the retailer's 800-strong fleet from mid-July and will transport goods between B&Q's distribution centres and stores.
The retailer is already planning a further 120 double-decker lorries for the second half of the year.
B&Q director of logistics Rick Jones said: "We're getting traffic off the road with these double-decker lorries because they carry as much as 50% more than those in our traditional fleet."
He added that the company is committed to reducing its road miles and carbon contribution, taking B&Q "another step closer" to its One Planet business ambitions. The fleet will also feature B&Q's One Planet branding.