He was sentenced to life in prison without the possibility of parole after reaching a plea deal with prosecutors.
Kohlhepp admitted killing four people at a motorcycle shop in 2003, and a married couple on his property in 2015.
In 2016 he was arrested for kidnapping a woman and killing her boyfriend.
As part of his plea agreement, which allowed him to avoid facing the death penalty, he also received a 30-year sentence for criminal sexual conduct and a 30 years for kidnapping.
Kohlhepp, 44, is a registered sex offender who had built a successful real estate business in Woodruff, South Carolina, 80 miles northwest of the state capital of Columbia.
In November 2016, investigators found a woman locked inside a metal shipping container on his 95-acre estate, after receiving a signal from her mobile phone.
It was described at the time by Spartanburg County Sheriff Chuck Wright as "a hellish place to be locked in hot weather. No lights, no windows, no air flow".
Kala Brown, who met Kohlhepp after he offered her work through Facebook, told officers that he had shot and killed her boyfriend in front of her.
She had been kept in chains for more than two months as Kohlhepp tried to convince her to fall in love with him, she described to US media.
On Friday, the Spartanburg County judge summoned the relatives of the victims in court, where they learned of the plea deal.
Police discovered human remains on his property belonging to her boyfriend, Charles David Carver, 32, as well as married couple Meagan Coxie, 25, and Johnny Coxie, 29, who had been buried there for more than a year.
The Coxies, who were identified by their tattoos, had a newborn child. They too had been hired to work on Kohlhepp's property.
During sentencing, Cindy Coxie - Johnny's mother - called the killer's actions "incomprehensible evil".
"Ultimately, good will triumph over evil," she continued, "God has put his finger on this. God has put a period."
Kohlhepp also confessed to killing four people at Superbike Motorsports in Spartanburg County after becoming enraged by an employee who mocked his experience as a biker.
Scott Ponder, Beverly Guy, Brian Lucas and Chris Sherbert were all shot and killed.
Court records show he had previously served a 15-year sentence in Arizona for kidnapping and raping his neighbour when he was a teenager.
"This is a big day, a long time coming," said Sheriff Wright, after the sentence was handed down on Friday.
Todd Kohlhepp, who was arrested after a woman was found "chained like a dog" on his property in South Carolina, has pleaded guilty to seven murders.