Kaine, 24, was charged Friday by prosecutors in St. Paul with fleeing on foot, concealing identity in a public place, and obstructing the legal process by interfering with a peace officer.
The obstruction charge is a gross misdemeanor, which carries a possible sentence of up to one year in prison and a fine of as much as $3,000.
Kaine was among counterprotesters inside the state Capitol's rotunda shortly after the "March 4 Trump" rally.
"Some of the counter-demonstrators, equipped with face and head coverings and goggles, broke away and attempted to enter the rally from the second floor staircase by pushing and shoving," a news release from Ramsey County Attorney John Choi said. "During the disturbance, they employed smoke bombs, mace and fireworks, thereby creating a chaotic and dangerous situation."
The group fled and were apprehended by police officers a few blocks away, officials said at the time.
A probable cause document says Kaine, who lives in Minneapolis, ran from a police officer, who caught him and knocked him down. It took several officers to detain Kaine after he scuffled with officers, the document says.
It was unclear whether Kaine has an attorney.
Seven others charged, two face felonies
Ramsey County declined to press felony charges against Kaine and five others, but St. Paul City Attorney Samuel Clark did further investigation and brought the charges against Kaine.
"In my mind, this has always been about making sure that people who seek to express themselves peacefully can do so free from fear of violence. That should be a bright line for everyone," Clark said.
Two other people arrested in connection with the incident were charged by Ramsey County prosecutors with felonies for allegedly using tear gas. They also face other misdemeanor charges.
Known as 'Woody'
CNN was attempting to reach a representative for the Kaine family and was not immediately successful.
Miryam Lipper, a spokeswoman for the senator, gave a statement to the Pioneer Press in St. Paul.
"Today's announcement of misdemeanor charges against Sen. Kaine's son contains no suggestion that he engaged in disruptive behavior while at the rally, but are instead focused on his actions as he was arrested after he left," Lipper said. "Tim and Anne support their son and hope the matter is resolved soon."
Asked to comment in March about his son's arrest, the senator and his wife would only say through a spokeswoman: "We love that our three children have their own views and concerns about current political issues. They fully understand the responsibility to express those concerns peacefully."
Linwood Kaine, who goes by "Woody," is the youngest son and second of Kaine and Anne Holton's three children. He graduated from Carleton College in 2014 after majoring in cinema and media studies, according to an alumni page.
He was never on the campaign trail during the 2016 presidential campaign, although his sister, Annella, appeared with at a few events and flew on the campaign plane.
The family's oldest son, Nat, a Marine, was deployed abroad just after Hillary Clinton named the Virginia senator as her running mate.