In a sit-down interview with Entertainment Tonight's Nancy O'Dell, the 50-year-old singer didn't say whether she knew of Armstrong's doping, but she did approve of his confession.
"I think that honesty is always the best bet and that the truth will set you free," Crow said.
"It's gotta be really hard to walk around knowing you're not telling the truth about something," she added.
According to ET Online, Armstrong and Crow dated from 2003 to 2006.
After years of denying he used performance-enhancing drugs, Armstrong came clean to Oprah Winfrey in a 90-minute interview last Thursday, telling the talk show host that his "mythic perfect story wasn't true."