The pilot is planned for the U.S. and Canada. Wal-Mart's fleet has about 6,000 trucks.
In an expansion from personal vehicles, Tesla CEO Elon Musk unveiled an electric semitractor-trailer Thursday that has a 500-mile range on a single charge and is electronically connected with a fleet's management system. The vehicle allows the driver to stand and puts the steering wheel in the center with a touchscreen panel on both sides of the driver. Musk said the truck is set to go into production in 2019, although the company has fallen far behind on its production schedule for the Model 3 mass market consumer vehicles.
Tesla shares closed up 0.8 percent Friday.
J.B. Hunt Transport Services announced earlier on Friday it has reserved "multiple" new electric semis just unveiled by Elon Musk.
A company could save tens of thousands of dollars if the Tesla Semi is, as Musk said, 25 cents cheaper to operate per mile than a standard diesel truck.
The average number of miles driven a year per large truck is just over 100,000, according to industry analysts. That means each Tesla Semi could save a company at least $25,000 a year.