Stearns was promoted after 15 years with the West Jordan Fire Department. Her official badge-pinning ceremony was held Wednesday, but she joined 11 other captains in the department April 1, said West Jordan Deputy Fire Chief Reed Scharman.
"To me, this is significant because it doesn't only show what women can do but what I can do," Stearns said.
After being mentored by other female captains and chiefs, she's eager to train the next generation of female firefighters and show, she said, "women are capable of any different role."
She takes on a title that once belonged to her husband, who died eight years ago this summer.
Bureau of Land Management Capt. Brett Stearns died when a tree hit him in the head and back during a training project in Colorado in 2009.
Although she'd wanted to be captain for years, it wasn't until she was promoted and someone said, "Congratulations, Captain Stearns," that it hit her, she said.
Previously, she'd only heard "Captain Stearns" in reference to her deceased husband.
"That was one thing that I wasn't expecting," she said. "It helped reconnect me with him."
Brett Stearns had been promoted to engine chief just before the couple married, and she watched him navigate the new leadership role.
"He would be very proud of me for being able to continue the name," Stearns said.
On her first day back after taking time off to mourn the loss of her husband, her crew responded to a call of a man fatally injured in a car crash.
The man was the same age Brett Stearns had been when he died, and as a new paramedic, it was the first time Joy Stearns had to pronounce somebody dead on the scene of an accident, she said.
"It was a hard day," she said. "But if I could make it through that, I could do this."
Those challenges built her into who she is now, Stearns said, and prepared her to lead and train other firefighters.
At the University of Utah, Stearns worked on a program to build resilience for firefighters as part of her master's degree in health promotion and education. She hadn't considered a career change after her husband died because of the support system of her fire station and because she had wanted to be a firefighter for so long.
Her interest in firefighting started after she saw "Backdraft" a film about Chicago firefighters investigating an arsonist as a 15-year-old, she said. She watched the movie the night before she needed to choose a professional to job-shadow, she said, and thought it was exciting. She shadowed a fire captain for the Salt Lake City Fire Department, then joined an explorer program for teenagers who are interested in firefighting and started training.
Because she started young at the fire station, she never felt like she had something to prove, she said.
Doing ride-alongs with other departments, Stearns occasionally faced what she called an "old-school mentality" about female firefighters.
But in West Jordan, she said, the station firefighters focus on one another's strengths. Someone may be able to drag a firefighter across a floor faster if need be, but she can fit into smaller, more confined spaces.
Scharman has known Stearns since she was hired and said he had high expectations for her career.
"Her knowledge, skills and abilities have always been at the top of whatever she's done," Scharman said. "Her testing [to apply for the captain position] wasn't a surprise to me. She's done well in everything she's tried."