McCready's body was found on the porch of a house in Heber Springs, Arkansas, on Sunday afternoon. She was pronounced dead at the scene "from what appears to be a single self-inflicted gunshot wound," the Cleburn County Sheriff's Office said in a statement.
Deputies had been dispatched to the area following reports of "shots fired," the sheriff's office said.
McCready, whose albums include "Ten Thousand Angels" and "If I Don't Stay the Night," had a complicated personal life, marked by a history of substance abuse, suicide attempts, family disputes and tragedy.
Last month, record producer David Wilson, the father of her youngest son, was found dead of an apparently self-inflicted gunshot wound in the same Arkansas town.
Some fellow musicians paid tribute to McCready on Twitter as news of her death spread. "My thoughts and prayers go out to Mindy McCready and her family today," country singer Tracy Lawrence tweeted.
Country star Carrie Underwood wrote, "I grew up listening to Mindy McCready... so sad for her family tonight. Many prayers are going out to them."
Born in Fort Myers, Florida, McCready learned to sing as a child at her local Pentecostal church. She moved to Nashville, Tennessee, to break into the country music business at the age of 18, according to allmusic.com.
She achieved early success with her 1996 debut album, "Ten Thousands Angels," which sold 2 million copies. Four other studio albums followed.
While successful in her career, McCready's personal life had begun to unravel in recent years.
In 2004 she was convicted of prescription drug fraud and placed on parole. Three years later she spent time in jail for violating her parole terms.
She had two young sons. Her first, Zander, was born in 2006. As her personal problems deepened, she became embroiled in a legal dispute over custody.
In November 2011, she left Florida with Zander and fled to Arkansas. McCready's mother, who had custody of the child, filed a missing person report against her daughter, and regained custody.
Her son with Wilson, Zayne, was born last year.
McCready appeared on the television show "Celebrity Rehab with Dr. Drew."
According to the biography posted on VH1's website as part of her appearance on the show, McCready said that she believed her only true addiction was to violent relationships.
In 2011 McCready appeared on HBO's show "Celebrity Close Calls" about life and death situations. That same year she also appeared on the network's "Celebrity Ghost Stories."
Her fifth album, "I'm Still Here," was released to acclaim in 2010.
The sheriff's office said McCready's body would be taken to the Arkansas State Crime Lab for an autopsy, adding that "the matter will be fully investigated."