Many think, for example, that it sets out to convert people and employs and tries to help only Christians. None of these is true.
The research was carried out as part of a new youth project to combat disengagement with global issues among 18 to 25-year-olds.
Katrin Owusu, head of youth marketing at Christian Aid, said: "We want to overcome the barrier of our name and get straight to the business of making change happen."
The new youth strategy, Ctrl.Alt.Shift, includes a three-year arts and culture programme, a new magazine and website, and opportunities to go on demonstrations and marches.
Matthew Reed, marketing director at Christian Aid, said: "Research shows that people can make assumptions about what the organisation is like, based on their previous conceptions of the church or of Christianity."
He said these misconceptions were as common among Christians as non-Christians. "The challenge is to get over misconceptions that are nothing to do with us. How people understand the word 'Christian' is defined by society, not us."