Melissa Stylianou was born September 30, 1976, in Toronto, Ontario, to a family with Irish and Greek Cypriot roots. She trained as an actor rather than a singer at first, studying at Toronto's Ryerson Theatre School from 1995 to 1998. Near the end of that program, at 21, a friend asked her to sit in with his big band at the Rex Hotel, Toronto's longtime jazz room; the evening redirected her entirely toward jazz singing, and she held a Friday-night residency at the Rex for the next five years. She took private vocal lessons with Carol Welsman in 1997 and 1998, studied arranging and theory at the Shelly Berger School of Music in 2000 and 2002, and attended the Banff Centre for the Arts' International Jazz Workshops, directed by Dave Douglas, in 2003 and 2004.

Stylianou fronted the swing/jump-blues group Slim's Lucky Number in Toronto and sang lead with the Canadian ensemble Spitfire Band from 2001 to 2006, alongside an appearance on the Treehouse TV children's program Foursquare. She self-produced her debut album, It Never Entered My Mind..., in 1999, followed by Bachelorette in 2001, both on her own Sleepin' Bee/Slim's Joint imprints with a small Toronto rhythm section. Touring took her to the Toronto, Montreal, Halifax (Atlantic Jazz Festival), and Brandon (Manitoba) jazz festivals, and by the mid-2000s she had drawn three consecutive National Jazz Award nominations for Jazz Vocalist of the Year (2003, 2004, 2006) plus one for Composer of the Year (2006). Her third album, Sliding Down (2006), closed out this Toronto period with a broader band featuring guitarist Kevin Breit and cellist Kevin Fox alongside her working rhythm section.

In November 2005, Stylianou relocated to New York City on a Canada Council for the Arts grant for professional musicians. She studied privately there with Theo Bleckmann, Garry Dial, Tom Schilling, and vocal pedagogue Jeannette LoVetri, and built working relationships with guitarist Ben Monder, bassists Chris Lightcap and Cameron Brown, guitarists John Hart and Steve Cardenas, and drummer Rodney Green. She appeared as featured vocalist on saxophonist Hayes Greenfield's Music for a Green Planet (2008) and on two tribute albums by percussionist Gregg Bendian's Mahavishnu Project revisiting the music of John McLaughlin's Mahavishnu Orchestra.

Her fourth album, Silent Movie (2012), was her first for Oded Lev-Ari's Anzic Records (catalog ANZ-0036), produced by Lev-Ari with a band of Pete McCann on guitar, Gary Wang on bass, Rodney Green on drums, and Jamie Reynolds on piano, plus guest appearances from Anat Cohen on bass clarinet, clarinet, and soprano saxophone and James Shipp on percussion. The record earned four and a half stars in DownBeat and a nomination as one of the magazine's Top 10 Rising Star Jazz Vocalists in its 2012 Critics Poll. She followed it in 2014 with No Regrets (Anzic ANZ-0046), again produced by Lev-Ari, with Bruce Barth on piano, Linda Oh on bass, Matt Wilson on drums, Billy Drewes on alto saxophone, and Anat Cohen returning on clarinet.

In 2015, Stylianou co-founded the close-harmony vocal trio Duchess with Hilary Gardner and Amy Cervini, modeling its three-part blend on the Boswell Sisters. Duchess released its self-titled debut that year, followed by Laughing At Life (2016/2017, with guest turns from Anat Cohen and Wycliffe Gordon), the Harmony for the Holidays EP (2018), Live At Jazz Standard (2020), and, after a six-year gap, the Rat Pack-themed A Marvelous Party (2026), expanded to a nonet with a small horn section arranged and produced by Lev-Ari. The trio won Vocal Group of the Year at the Jazz Journalists Association Awards in both 2021 and 2022 and took Best Vocal Group in JazzTimes' 2021 critics poll.

Stylianou's most recent leader date, Dream Dancing (2022, Anzic ANZ-0080), paired her with guitarist Gene Bertoncini and bassist Ike Sturm in an intimate, self-produced standards trio; DownBeat gave it a full five-star review. She continues to perform with Duchess and as a leader, and maintains a private voice studio in New York City.

Stylianou works as an interpreter more than a stylist, moving without strain between the Great American Songbook and material by Johnny Cash, Paul Simon, James Taylor, Björk, and Joanna Newsom, often finding a jazz phrasing inside songs that were never written as jazz. Pianist Fred Hersch has praised her "gorgeous instrument, superb musicianship, and great taste," and critics have repeatedly singled out her phrasing and emotional directness over vocal display. She operates comfortably in two very different modes: the solo-spotlight balladry of her leader dates, built around a warm, velvety upper register, and the disciplined three-part blend of Duchess, where individual interpretation gives way to close-harmony ensemble singing in the Boswell Sisters tradition. Reviewers at All About Jazz followed her records across two decades, from her early Toronto sessions through Silent Movie and No Regrets, consistently returning to her "articulate assurance" and "fine sense of phrasing."