Underwood, 32, said she will be meeting with military families to thank them for their service, reported Billboard magazine.
"I'm honoured to be able to join Carnival Cruise Line and Operation Homefront to lift up these soldiers and their families," Underwood said.
"I am really looking forward to meeting them on my tour and for the opportunity to personally thank them for all they do for our freedom. I feel country music has always been very close and very supportive of military members and their families. I feel like this is just another really cool opportunity to say thank you.