The high-profile but brief trial took place in Ho Chi Minh City under heavy security, reports say.
The trio were given jail sentences of between four and 12 years.
The government, which does not allow freedom of expression, has been under pressure from bloggers over corruption cases and human rights issues.
The three were accused of posting political articles on a banned website called Free Journalists' Club, as well as articles critical of the government on their own blogs.
Nguyen Van Hai, who uses the pen name Dieu Cay, received the longest sentence of 12 years.
The case of Dieu Cay, who was a soldier before he became a dissident writer, was raised by US President Barack Obama earlier this year.
Former policewoman Ta Phong Tan, who also wrote a blog called ''Justice and Truth'', was sent to jail for a decade. In July, her mother died after setting herself on fire in apparent protest against the detention of her daughter.
The third dissident writer, Phan Thanh Hai, was jailed for four years.
In a statement, the US embassy in Hanoi called on the Vietnamese government to free the group.
"We are deeply concerned by reports that the Ho Chi Minh City People's Court convicted and sentenced blogger Dieu Cay to 12 years in prison for peacefully expressing his political views," the statement said.
Activists have accused the government of stepping up a crackdown against bloggers and peaceful activists.
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