She performed at charity events and fairs around the province, in addition to the BC Summer Games recording their theme song, "Reach for the Stars".

She went on to appear on the Variety Club show singing a duet with Bob McGrath, sang the first set of songs at the Molson Indy (a major car race), and entertained on New Year's Eve at Planet Hollywood at the age of 12.

Johnson auditioned for the Disney Channel original series So Weird, which was casting for a lead actress who could also sing for the final season of the show.

Her co-write from Disney’s So Weird, "Dream About You" charted six different times and came in at number one in "Radio Play Favorite Song Requests" for "The Most Listened-to New Tracks on Broadband Talent Net" on November 11, 2000.

Also "Sunshine Reigns", an early credited co-write with songwriters Trevan Wong and Doris Young, charted at number three on July 22, 2000.

[12] In the year 2000, a song performed by Johnson entitled "Everything (Feels Like New)" was featured in the Disney Channel Original Movie The Other Me, starring Andrew Lawrence.

She promoted the project by performing a few verses in an impromptu a capella that aired on Disney Channel during her Express Yourself interview feature that was highly circulated during commercial breaks at the time.

[16] Select scenes from their original audition tape were released as part of the bonus features on the Instant Star, Season 1 DVD boxset.

Throughout 2004, Johnson made various appearances on Canadian television series including The Chris Isaak Show, The Collector, and Cold Squad where she performed two original songs as twins Dierdre and Tricia Spence.

The first audition tape Executive Producer Stephen Stohn received was Johnson's via Canadian Singer-songwriter and actress Belinda Metz, and he was convinced she was perfect for the role.

On August 28, 2007, the show received three more Gemini Award nominations, in the category of Best Children's or Youth Program or Series, including another for Best Performance (Alexz Johnson, in the episode, "I Fought the Law").

She co-wrote five of the songs on the first season's soundtrack, including "24 Hours", "Let Me Fall", "Criminal, "Skin", and "That Girl", which Johnson had written before when she was fourteen.

In early 2006, Johnson announced she was leaving the indie Canadian label Orange Records that released the first two soundtracks to Instant Star, in search of something to showcase her as an artist and not her fictional counterpart, Jude Harrison.

He's a cynical know-it-all, like Dennis Miller with black fingernails; she's like Parker Posey with raccoon mascara.."[18] In 2007, Johnson starred in the Lifetime film Devil's Diary, for which she received a Leo Award nomination, in the category of Best Lead Performance by a Female in a Feature-Length Drama.

In writing songs for the album, she worked with UK writers Martin Terefe and Sacha Skarbek as well as producer/songwriter Brio Taliaferro.

In her MySpace blog of February 15, 2008, Johnson indicated that she was planning an extensive tour around her new album, saying of her songs that, "I can't wait to perform them live!

She stated that the filming—which included a dramatic scene in which her two characters conflict through astral projection, leading to a fall off a cliff and into a waterfall—was so mentally and physically demanding, that she felt like she could never take on another role like it again.

Johnson later gave clarification on her website that launched August 11, 2009,[21] saying "Epic has released over a third of their artists from their contracts and, la dee da...

[22] Johnson informed her fans through her Twitter account and her official website that all the songs from Voodoo would be remixed by the Demolition Crew due to lack of airplay.

Lovato has spoken several times about Johnson being her inspiration to start a career in music, while Furtado spoke about her single "Look at Those Eyes" calling it "an event".

[24] In June 2011 it was announced that Johnson would sing on the opening theme song of the television series Degrassi: The Next Generation Season 11.

Johnson announced her plans to release an EP featuring new material, and confirmed on October 29 that she was in New York filming the music video for her new single "Skipping Stone".

Skipping Stone was released on January 24, 2012, that same day she launched a Kickstarter Campaign in order to raise funds for her upcoming U.S. tour.

[28] She worked with Bleu, Boots Ottestad, Wax Ltd, Jamie Hartman, Theo Katzman, and her brother Brendan James Johnson on writing the Extended-Play.

[29] Johnson launched a joint North American tour with Charlene Kaye, Misty Boyce, and Jay Stolar in the spring of 2013.

[30] On Christmas Day of 2013, she released the lead single from Heart, titled "American Dreamer", initially only to fans who had already donated, and pledged.

[38] Pledgers received digital copies of Johnson's sophomore album Let 'Em Eat Cake one week before the official release date of October 14, 2014.

Alexz Johnson could be seen in 2001 during her episode with Disney Channel's Express Yourself citing Celine Dion, Whitney Houston, Mariah Carey, and Sarah McLachlan as vocal influences.

[63] In 2002, she performed as the opening act at Wayne Gretzky's celebrity dinner and auction, held in Edmonton, Alberta, to raise funds for the Ronald McDonald children's charity.

[65] In 2021 Johnson teamed up with Cameo.com, in which fans can purchase personal request videos, announcing that partial proceeds will benefit the Canadian Cancer Society.