Born in Brooklyn, New York, on June 24, 1958, Troccoli moved at age three and was raised in the small town of [[Concord, New Hampshire]Islip, Long Island, graduating from East Islip High School . At 15, she lost her father to colon cancer. She also lost her mother to breast cancer in 1991, shortly before the release of her album Pure Attraction and its mainstream chart selection, "Everything Changes." Before recording and releasing the album, Troccoli had taken a five year break from the music world to do some "soul searching" and deal with her bulimia.

After graduation, she attended the Berklee College of Music in Boston] for a year, studying jazz and Opera, before returning home to attend college in the Long Island region. While working to pay her college bill, she committed herself to Christendom (1978), and her alto voice gained prominence when she opened for Ed Nalle's group GLAD in 1980 during a concert in the area.

Nalle assisted Troccoli in her career, helping the young artist record demos which would be given to Michael Blanton and Dan Harrell (Amy Grant's brother-in-law), who formed the Reunion label to start her career in 1982 with Stubborn Love. A second album, Heart and Soul, was released in 1984 and gave her first Grammy nomination a year later, followed by Images in 1986. Troccoli also provided backing vocal for Taylor Dayne's song "I'll Be Your Shelter" in 1989/1990.

After her mother's death, she paired with Reunion again in 1991 with Pure Attraction, which launched her on the national charts with the single "Everything Changes," which peaked at #14 on the Billboard Hot 100. But ironically, it was "Help Myself To You" which became her first #1 hit in her ten-year career, and began a string of GMA Music Awards nominations, including numerous attempts at Female Vocalist.

Numerous hit songs came afterwards, including 1994's "My Life Is in Your Hands," jointly written and composed with Bill Montvilo, which defined her career and inspired the devotional book of the same title, written in 1997, and 1995's "Go Light Your World," which began the rise of writer Chris Rice and was used for charity efforts that year.

In 1996, Troccoli was featured on the Beach Boys's now out-of-print album Stars and Stripes Vol. 1, singing lead vocals on a cover of their 1969 song "I Can Hear Music," itself a cover of a Phil Spector song. The Beach Boys sing on the track as well, providing harmonies and backing vocals.

With no success at the GMA Music Awards from 1992 until 1997 (over 15 nomination attempts), she was nicknamed "Christian music's Susan Lucci" for failure to win even one award.

The release of Love & Mercy in 1997 changed her career. One song, "A Baby's Prayer," written and composed after she and collaborator Scott Brasher had observed the abortion issue and Brasher's viewing of Holocaust documentaries, made her a well-sought speaker in 1998, and with the Inspirational Song award, she finally won her first GMA Music Award.

Her 1998 release Corner of Eden resulted in an Inspirational Album award at the GMA Music Award in 1999, her second GMA Music Award.

Her second Grammy nomination came in 2003 with her album The Heart of Me. But it was marred by controversy, as BMG was the record label to which all five nominees for the award were signed.

Troccoli was voted the fourth most influental Christan woman in America by Todays Christian Woman Magazine.

In addition to her musical activities, Kathy wrote several Christian books in collaboration with Dee Brestin, and also wrote some of her own as well. These books included Hope for a Woman's Heart, Falling in Love With Jesus (with Brestin), Living in Love with Jesus (with Brestin), Forever in Love with Jesus (with Brestin), Am I Not Still God?, My Life Is in Your Hands, and Seven Celebrations for the Soul. She likewise became a frequent popular speaker, and musician, for Christian organizations and at well-known Christian events such as "Women of Faith," "Heritage Keepers," and "Time Out for Women Only," as well as several cruises that are known to take place annually in February. Kathy performed at the 1999 Fiesta Bowl National Championship as well as the 1999 National Day of Prayer.

Over the years, Kathy has appeared on The Tonight Show, Live with Regis and Kathie Lee, The 700 Club, Entertainment Tonight, among others. She also appeared on Focus on the Family's video for teens, Sex, Lies, & The Truth, speaking out on the importance of sexual purity.

Notably, Kathy auditioned for the role of Eva Perón in the film version of Evita, competing against well-known pop singer Madonna. She finally lost the role to Madonna after three call-back auditions.