Aguilar pleaded guilty in November 2022 to one count of accessory to murder after the fact and three counts of false statement or representation.
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The sentence was the maximum time behind bars behind she could face.
Aguilar, 25, admitted to helping her boyfriend, Specialist Aaron Robinson, dismember and dispose of Guillen's body near the Leon River in 2020.
"Our hope is that today's sentence brings a sense of relief and justice to the Guillen family, who have endured such pain throughout these past few years," Jaime Esparza, U.S. Attorney for the Western District of Texas, said. "Ms. Aguilar's actions were indefensible, and she will now face the maximum penalty for the choices she made."
Guillen, a 20-year-old Fort Hood Army Specialist from Houston, disappeared in April of that year. Her remains were found two months later.
Fort Hood was renamed Fort Cavazos in May, after the Army's first Hispanic four-star general Richard Edward Cavazos.
Robinson was one of the last people in touch with Guillen based on cellphone records, according to court documents.
He died by suicide before her body was found.
A grand jury indicted Aguilar on federal charges after a Texas judge denied her attorneys' motion asking that her confession in the crime be thrown out.
SEE ALSO: Vanessa Guillen's family on Army sexual assault data: 'You don't sign up to get sexually assaulted'
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The indictment also accused Aguilar and Robinson of making false statements to prevent themselves from being charged with any crime.
Prosecutors said Guillen was bludgeoned to death with a hammer by Robinson in the armory of the Killeen, Texas, military base, on April 22, 2020, according to the criminal complaint.
After her death, Guillen's family pushed the most powerful military in the world to change because of what happened.
Before she was killed, her family said she told them she was being sexually harassed by a superior.
MORE: Vanessa Guillen: Family's fight for justice could result in historic US military changes
A U.S. Army investigation determined that Vanessa Guillen was sexually harassed by a supervisor, and that the leaders in her unit did not take appropriate action after she stepped forward.
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The family has since sought to reform the way the military handles sexual assault and harassment cases since her death.
"Today justice prevailed for my clients, Vanessa Guillen's family, Vanessa's friends and our country!" Natalie Khawam, the Guillen family attorney, said in a statement. "Judge Albright sentenced Cecily Aguilar to 30 years. We finally have closure in this case. I want to thank the US Attorney's office, the Texas Rangers and all the law enforcement that gave their all to prosecuting this case. We are grateful for everyone that supported us over the last 3 years. It was long tough road, but we can finally celebrate Justice for Vanessa!"
Watch the ABC13 Original "Vanessa Guillen: Remember Her Name," which takes a look back at her life, has exclusive interviews with her family and takes a deeper dive into their push for justice
Vanessa Guillen: Remember Her Name