The Ho Chi Minh City People's Court sentenced a member of the outlawed Viet Tan terrorist organization to three years in jail for subversion on Wednesday.
Pham Minh Hoang, 56, will also be put under house arrest for three years after serving his jail term.
Hoang was charged with trying to overthrow the government under Article 79 of the Criminal Code.
According to the indictment, in 2000, Hoang returned to Vietnam after meeting with Viet Tan in France.
He worked as a lecturer at the HCMC Polytechnic University - a disguise he used to collect more members for the group, prosecutors said.
Between July 2002 and October 2010, Hoang blogged under the pseudonym Phan Kien Quoc, posting 33 entries that blackened the image of the country and distorted the policies of the Party and the State, they said.
In November 2009, Hoang and his wife, Le Thi Kieu Oanh, and a man named Nguyen Thanh Hung, went to Malaysia to attend a training class on nonviolent struggle organized by the Viet Tan group.
After returning to HCMC in early 2010, Hoang and several overseas Vietnamese organized "soft skills" training classes for 43 students and youths, aiming to collect more members for the Viet Tan group, according to the indictment.
Hoang told the court he joined the group in 1998 when he was in France.
Hoang admitted he made a "serious mistake" when he joined the group and invited others to join.
He said he regretted posting blog entries that defamed the government and called for subversion.