The girl band - Perrie Edwards, Jade Thirlwall, Leigh-Anne Pinnock and Jesy Nelson - arrived in Liberia today to see how money raised helps the local community.
For the girls' first visit, they stopped off at a hospital to see how malaria affects children who don't have a mosquito net to sleep under.
They tweeted: "First day in Liberia with @sportrelief. We're looking to seeing to Sport Relief cash in action x."
Little Mix's trip to Liberia follows their announcement earlier today that they will be releasing a version of Cameo's 1986 smash hit 'Word Up'.
Their rendition, which will be available to buy on 17 March, will be the official single for Sport Relief 2014.
Perrie said: "We've all seen people push themselves and do incredible things for Sport Relief so it's a dream come true to be releasing the official single this year. We can't wait for you all to hear it!"
Jade added: "We are so happy to be part of Sport Relief and want to help raise as much cash as possible for some truly amazing causes."
Watch Little Mix announce their single details in the video below: