A statement from Nokia said this was the company's 38th commercial 5G contract, 20 of which are with named customers.
It said Nokia's 5G AirScale would be deployed across Japan, to provide 5G RAN to businesses and consumers.
Nokia claimed the 5G investment would benefit consumers by bringing them a 5G enhanced Mobile BroadBand (eMBB) service, with 5G Ultra Reliable Low Latency Connectivity (URLLC) and enhanced Machine Type Communication (eMTC) enabling multiple new applications and services for industries.
"We are committed to help SoftBank launch their commercial 5G network."
Nokia said "As an existing supplier of multiple technologies to SoftBank, Nokia's selection for 5G Radio re-enforces the strong relationship between the two companies, as SoftBank turn to Nokia's end-to-end portfolio for 5G.
"Nokia's 5G AirScale supports multiple frequencies, in both distributed and centralised architectures, giving SoftBank tremendous flexibility in its network evolution."