Alexander James McLean was born on January 9, 1978, in West Palm Beach, Florida, to Denise (née Fernandez, now Solis) and Bob McLean. He is of Cuban and German ancestry on his mother's side and Scottish, Irish and English on his father's side. He is an only child because his twin sisters died during childbirth. He was raised by his mother and grandparents (Ursula and Adolph) as his parents divorced when he was four years old.
As a kid, McLean had a speech impediment, which made him lisp and stutter.
He discovered his love for performing and started to pursue a career in acting, dancing and singing. When he was four, McLean began to focus on his love for dance, so his mother signed him up for dance lessons every day for two hours. He took ballet for four years, jazz, tap, hip hop, rhythm tap, rhythm hip-hop, contemporary, ballroom, salsa, merengue and gymnastics. His mother then got him into modelling when he was around five for a few years, doing J.C. Penny's catalogues and runways. At age six, McLean was part of a school play, Snow White and the Seven Dwarfs, in which he played Dopey, at Unity of Delray Beach church and school. He also appeared in more traditional musicals such as The Nutcracker, The King and I and Fiddler on the Roof before the age of 11. By the time he was 12, he had performed in many classic school plays.
In addition to singing and acting, he was a serious dance student learning everything from jazz to ballet to hip hop.
In January 1986 at 8 years old, McLean acted in his first role as Little Mike in the 1986 film Truth or Dare?.
In 1990, McLean, his mother and grandparents moved to Kissimmee, Florida, to pursue his acting and singing career. He attended a private acting school, the Florida Academy of Dramatic Arts, for four years, acted in the drama club and in small plays, and modeled periodically.
In 1991 McLean landed a role on the Nickelodeon comedy series Hi Honey, I'm Home! as a kid named Skunk. However, he was cut from the show due to being too tall. His only known appearance on the show is in the pilot episode, which Nickelodeon aired in 1999 as part of its birthday celebration.
When he was 13 years old, McLean tried out for Star Search, but never received a call back from the show. He later saw an ad in the newspaper for a Latin festival and since his grandfather has Latin roots, he decided to audition. He later learned that he had won first place and a $1,000 prize. The producer of the festival hired him to perform a 45-minute one-man show. He did a puppet show which also showcased his singing and dancing. At the Latin festival, he met a young Howie Dorough (Tony Donetti at the time) through a mutual vocal coach.
In junior high, McLean won a part in Nickelodeon's series Welcome Freshmen, which began his ongoing work relationship with Nickelodeon and the Disney Channel. He also appeared on the Nickelodeon show GUTS and a Muppets commercial. It was during one of his auditions for the former that he met Howie D. and Nick Carter, lacing together the roots of the group that was to become Backstreet Boys.
In March 1992, there was an ad in the newspaper seeking for young men between the ages of 16-19 for an audition of a new music group. Despite being 14 years old, he auditioned for the group. By April 1992, McLean was officially the first member of the group that would become the Backstreet Boys. After three years at Osceola High School, he finished his final year of high school with a tutor on the road after joining the Backstreet Boys.