Katharine McPhee’s New Bikini Bod

Born in Los Angeles, California, McPhee moved with her parents and sister to Sherman Oaks at age 12. McPhee has been singing since the age of two. Her mother, Patricia Burch McPhee (stage name Peisha Arten, a vocal coach and accomplished cabaret singer, recognized her daughter's musical talent and decided to train her. Her father, Daniel McPhee, is a television producer and her older sister, Adriana Burch McPhee (born June 30, 1982) is an aspiring producer as well.

McPhee graduated in 2002 from Notre Dame High School. At Notre Dame High School, McPhee was a swimmer and a thespian. Afterward, McPhee attended Boston Conservatory for three semesters, majoring in musical theater. She left the college on the advice of her manager, and returned to Los Angeles to try out for television pilots. In a People news article, it was reported that she was rejected in "only 195 out of 200 auditions." She had a small role as "Paramount Girl" in the 2007 musical film Crazy, based on the life of Hank Garland. McPhee was also part of a failed mall-based MTV soap opera entitled You Are Here, playing the older sister of a more popular younger sister.

McPhee has struggled with eating disorders in the past. She told People (magazine) that at age 13 she began starving herself and exercising compulsively, and became bulimic at age 17. During her run on American Idol, she lost 30 pounds. After a period of about five years, she began treatment after qualifying for American Idol. .After seven years of illness, she finally entered a three-month rehab program. Now, as she told Teen Vogue in May 2007, "I eat whatever I crave—I'm just really careful about portions."