Among those convicted are student leader Lesther Aleman and prominent opposition leader Dora Maria Tellez.
Nicaragua sentenced seven other opposition figures to long prison terms for “conspiring to undermine national integrity”.
Those convicted Thursday were among dozens of arrests ahead of last year’s election, which saw President Daniel Ortega win a second consecutive term in polls dismissed as illegitimate by international observers.
Among them is Lesther Aleman, a student leader who stood up to President Daniel Ortega in 2018. He was given a 13-year term.
Dora Maria Tellez, a former Sandinista rebel, was also convicted. She had led an assault on the National Palace in 1978 during the Somoza family dictatorship and held members of Congress hostage in exchange for the release of rebel prisoners. Tellez, who broke from Ortega’s party in 1995 and became leader of an opposition group, was sentenced to eight years in prison.
Rights groups have dismissed the lawsuits, held in the infamous Chipote jail, as a sham.
Aleman’s mother, Lesbia Alfaro, decried her son’s trial as “nonsense, a lie, a circus”.
“He’s not a terrorist,” she said.
Among the opposition figures jailed last summer were seven potential candidates for Ortega for president. On Wednesday, former presidential hopeful and journalist Miguel Mora was sentenced to 13 years in prison.
Thousands of people have fled into exile since Nicaraguan security forces violently suppressed protests in 2018.
Ortega said the protests were in fact a coup attempt with foreign support. Many of those on trial have been accused of working with foreign powers for his overthrow or encouraging foreign nations to impose sanctions on members of his family and government.
Ortega ruled Nicaragua from 1979 to 1990 after leading a rebel army that overthrew US-backed dictator Anastasio Somoza.
He returned to power in 2007 and was re-elected three times as critics say he gradually consolidated power and stifled dissent.
The United States and the European Union have imposed sanctions on Nicaragua, the poorest country in Central America, for human rights and election-related violations under Ortega.