The Obviously hitmaker shared a YouTube.com video with his online followers to promote Earth Hour, a mass participation event which encourages people to conserve energy.
In the clip, Fletcher, who is dressed in a panda costume, urges fans to join the movement.
He says, "Our lovely planet here is going through a lot of environmental changes at the moment and it's all because of things that people like you and me and all the human beings in the planet are doing to it... It's super easy to take part and get involved, all you need to do it turn your lights off...
"Me and all the MCFly boys are taking part, we're going to be 'doing it in the dark' and we would love it if you did too... We have only got one of these things (Earth) and it's really important that we take care of it."
Earth Hour takes place worldwide on Saturday (23Mar13) when 7,000 people across 152 cities will turn their lights off for one hour at 8.30 pm local time.