The two NFL legends showed off their sweet voices in a new vid this week ... and it was all to help raise money and awareness for those battling cancer during the COVID-19 pandemic.

FYI ... the Hall of Famers are part of the NFL's Player's Choir, which is a group of about 20 current and former footballers who have some serious pipes.

And, at some point this month, they joined up for a virtual, socially-distanced rendition of "This Little Light Of Mine" to help out the American Cancer Society ... and it's amazing.

Check out the vid ... the NFLers smashed the tune for about three minutes -- and the fact that it was all for a great cause made it even sweeter.

The ACS says the cancer community has had to deal with some serious and unique needs during the global pandemic ... and it says vids like this one can help raise donations through their "Share The Light" campaign.