NCA officials said boys as young as 14 have been targeted with "sextortion" scams on social networks including Snapchat and Instagram.
Criminals trick them into sending sexual images - and then threaten to share the pictures with their family, friends and school unless they pay about £100.
While most victims of child sexual exploitation are female, the NCA said 90% of online sextortion victims are boys aged 14 to 17.
In some cases, those affected have taken their own lives out of fear the images will be shared.
Marie Smith, a senior manager at the NCA's child exploitation and online protection command, called the abuse "extremely disturbing".
As part of an NCA awareness campaign, she urged victims: "Do not pay - stay calm. We can help. If you pay once, they will just demand more."
Sextortion 'unimaginably cruel'
Most of the offences are committed by people from West African countries, including Nigeria and the Ivory Coast.
"Nothing is off the cards and we hope to hold these criminals accountable," Ms Smith said.
NCA director of threat leadership Alex Murray said: "Sextortion is unimaginably cruel and can have devastating consequences for victims.
"This campaign will help empower young boys, giving them the knowledge to spot the dangers posed by this crime type and how to report it.
"It supports them to understand that if it does happen, it is never their fault. It will also take the advantage away from the criminals responsible, whose only motivation is financial gain.
"Sadly, teenagers in the UK and around the world have taken their own lives because of 'sextortion', which has been a major factor behind launching this campaign."
Last year alone, the NCA's CEOP safety centre received 380 sextortion reports. In the first five months of 2024, UK police forces recorded an average of 117 monthly reports involving under-18s.
And in the US, the National Centre for Missing and Exploited Children received more than 28,000 sextortion reports globally in 2024 - up from 26,718 the previous year.
Most of the offences are committed by people from West African countries, including Nigeria and the Ivory Coast.
"Nothing is off the cards and we hope to hold these criminals accountable," Ms Smith said.
NCA director of threat leadership Alex Murray said: "Sextortion is unimaginably cruel and can have devastating consequences for victims.
"This campaign will help empower young boys, giving them the knowledge to spot the dangers posed by this crime type and how to report it.
"It supports them to understand that if it does happen, it is never their fault. It will also take the advantage away from the criminals responsible, whose only motivation is financial gain.
"Sadly, teenagers in the UK and around the world have taken their own lives because of 'sextortion', which has been a major factor behind launching this campaign."
Last year alone, the NCA's CEOP safety centre received 380 sextortion reports. In the first five months of 2024, UK police forces recorded an average of 117 monthly reports involving under-18s.
And in the US, the National Centre for Missing and Exploited Children received more than 28,000 sextortion reports globally in 2024 - up from 26,718 the previous year.
