Just more than half (55%) of those said it had been sent by mobile phone.
The most common ways of communicating sexually explicit material are via Bluetooth, by uploading it on to a personal website or social networking site, or by e-mailing and texting it to individuals, Beatbullying said.
Some 45% of teenagers who had received explicit content said it had come from another teenager, and 23% said it was from their boyfriend or girlfriend.
Nearly one in three said they were using an online messaging service when content of a distressing sexual nature was introduced.
A higher proportion of women than men said this was the case - 31% as opposed to 24%.
Last year, psychologist Dr Tanya Byron carried out a review of children's use of technology and recommended a taskforce be set up to spearhead protection measures in schools and the community.
But she said the role of parents was absolutely vital in managing teenagers' access to potentially harmful material.
In response, the government set up the UK Council on Child Internet Safety, an umbrella group of organisations working in the field.
Beatbullying's chief executive, Emma-Jane Cross, said new technology was facilitating sexual contact between teenagers and that this needed to be addressed.
"We don't want to inhibit young people in their exploration of sexuality, but it is important that parents and schools are aware that 'sexting' is a significant issue among our children and young people, so together we can act to stop this kind of behaviour before it escalates into something far more problematic."
She said prominent cases of teenagers who had harmed themselves after experiencing such bullying had led to a debate in the US and Australia.
Schools Minister Diana Johnson said the government was committed to tackling all forms of bullying, including working with technology companies on the misuse of new formats.
"It is important that young people being bullied know that they can report it and that it can be stopped.
"We are supporting parents to have the confidence to engage with their children on the challenges of modern life - including sex and technology.
"We are also supporting teachers to identify and intervene as early as possible."
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