Wayne Hudson, 45, from Park Street, Kidderminster, targeted his victims on social media where he posed as a 15-year-old boy.
He pressured girls, who were aged between 12 and 13, into sending him indecent photographs and videos of themselves and threatened to expose them in order to obtain more images.
Hudson also communicated with them in a sexual manner and sent indecent photos of himself.
But his offending came to light when one of his victim's mothers saw text messages on her daughter's phone from Hudson.
He had five victims in total who were located around the country including Staffordshire.
Hudson was imprisoned for six years and eight months at Worcester Crown Court on Tuesday after he pleaded guilty to six offences.
He admitted three counts of causing, or inciting, a child under 13 to engage in sexual activity, and three counts of sexual communications with a child.
However he entered no pleas for a further three counts of causing or inciting a child under 13 to engage in sexual activity.
Karen Walton, from the Crown Prosecution Service, said: "Wayne Hudson hid behind a computer and developed three social media personas to target girls as young as 12.
"He was fully aware of their ages, having asked early on in the conversations, yet he enticed them to send him naked photos and videos and blackmailed them for further images.
"I would like to thank the victims for their bravery in coming forward to ensure that Hudson has been jailed for his actions."
He was also made subject of a Sexual Harm Prevention Order.