Colleen McKenna was born May 31, 1948, to Joseph and Ruth O'Shaughnessy in Springfield, Illinois. It was not long until her family moved to Pittsburgh, Pennsylvania, where Colleen was influenced by "Little Joe Cartwright" and began to write her own scripts to the popular television show Bonanza. In eighth grade, Colleen mailed in her three best scripts with the intent to see them on television. Bonanza influenced McKenna, teaching her how to develop the sequence of plot. After high school, McKenna continued her education at Slippery Rock University where she earned a B.A. in elementary and special education. She furthered her education at Carnegie Mellon University and University of Pittsburgh to pursue teaching.

While teaching third and fourth grade at a Bethel Park Elementary School in Pittsburgh, Colleen married Frank McKenna III, an attorney, on March 25, 1972. Throughout her experience teaching, McKenna utilized her interest in writing to create plays for her classes. But, it was not long until Colleen and Frank had children, causing McKenna to put her love of teaching on hold. Together they had four children: Collette, Jeff, Laura, and Stevie. After the birth of her children, McKenna began writing children's literature when her husband left on a three month long business trip. To improve her writing, she took a children's literature course and learned that writing must based upon past experiences. Following the course, McKenna knew that her own children and family lifestyle was what she knew best and she would use her own knowledge to guide her writing. McKenna's secret to writing was to focus on character development rather than plot. In an interview, McKenna said that she feels the personalities of the individual character will create the plot on their own. Using her experiences and the techniques obtained from her writing course, McKenna was able to create many stories that would appeal and relate to children.

In the late 1980's McKenna began establishing her first set of children's books called, the "Murphy" Series. Her first novel was written in 1988, entitled Too Many Murphys. The "Murphy" series of texts were based upon McKenna's own four children from the perspective of her oldest daughter, Collette, and is also her most well-known string of books. The story is one that children with siblings can sympathize with and all children can relate to the experiences and typical situations Collette faces with her friends and in the classroom. In Too Many Murphys,Collette thought to herself, "Mrs. Byrnes was probably sure she had been around too many Murphys for one day." Collette had always been embarrassed by her family, especially in social settings. McKenna continued her sequence of novels with seven others including Fourth Grade is a Jinx in 1989, Fifth Grade Murphy's Island in 1990, and Mother Murphy in 1992. According to a Kirkus Review of Mother Murphy, "In this wholesome, funny story about that increasingly atypical phenomenon, a nuclear family where the mother stays home, McKenna gets it just right. A welcome addition to the series about Collette and her loving family." Additionally, in 1992 McKenna received an Award of Excellence from Slippery Rock University for her writing accomplishments. The following year, McKenna ended her first succession in 1993 with Camp Murphy.In the midst of writing her "Murphy" Series, McKenna also wrote other books such as the "Cousins" Series and Merry Christmas, Miss. McConnell! Throughout her writing career McKenna was able to achieve success writing about her family and the everyday obstacles children face in school and with their friends.

After the completion of her first series, McKenna moved away from writing about her own life and wrote books to coincide with hit television show, Dr. Quinn, Medicine Woman. She wrote two novels New Friends and Queen of May in 1995 and 1996 respectively. The books were based upon a doctor and her family living during the Civil War period. Each plot draws on Dr. Quinn's daughter and the conflicts she faces within school. During this time period, McKenna participated in the Friends' Fest in New Orleans were she helped to encourage and support young writers. With each new book and series, McKenna was able to further develop her characters and communicate to her readers.

Four years later in 2000, McKenna began writing young adult novels once again and started another series of books called the "Gordie Barr" Series. It is about a young boy, Gordie, and his best friend, Lamont, and their troubles within the third grade classroom. The series began with Third Grade Stinks! and was followed by two more. In Something About the Author,reactions to her writing were summarized: "Reviewers have called her books warm, funny, and insightful..." Writing about familiar subjects allows McKenna to achieve recognition by the critics for the reality portrayed within her writing.

Today, McKenna's children are all grown up and she still resides in Pittsburgh with her husband. In her hometown she teaches catechism at her local church, St. Joseph's. She also mentors at Seton Hill University as well as teaches at the Institute of Children's Literature. Along with her volunteer work, she is a member of the Society of Children's Book Writers and Illustrators. In 2005, McKenna joined Friends' Fest again and commented on her writing style. According to an interview with Matt Berman of the New Orleans Times-Picayune, McKenna stated, "In my writing I never set out with a moral message, I just have a story about everyday life, and with that comes humor and some type of message." McKenna spends her time talking to children about how to develop a storyline, how to create pictures to enhance your writing, and shares tips with students about reading. She is a strong advocate of reading and writing and aims to share her love with young children. As a writer, McKenna has written twenty-one books and sold over three million copies. She persistently reaches out to children with her continuously developing characters and story lines that connect to all readers.