Whitney was a mezzo-soprano. Her vocal range extended from G below middle C to high B-flat; she could belt out to treble F. She was third on MTV's 22 Greatest Voices, and sixth on Online Magazine COVE's list of the 100 Best Pop Vocalists with a score of 48.5/50. In 2008, Rolling Stone listed Houston as the thirty-fourth of the 100 greatest singers of all time, stating "Her voice is a mammoth, coruscating cry: Few vocalists could get away with opening a song with 45 unaccompanied seconds of singing, but Houston's powerhouse version of Dolly Parton's "I Will Always Love You" is a tour de force." Describing Whitney's voice, Mariah Carey states "[she] has a really rich, strong mid-belt that very few people have. She sounds really good, really strong." While in her review of I Look To You, music critic Ann Powers of Los Angeles Times writes, "[Whitney's voice] stands like monuments upon the landscape of 20th century pop, defining the architecture of their times, sheltering the dreams of millions and inspiring the climbing careers of countless imitators," adding "when she was at her best, nothing could match her huge, clean, cool mezzo-soprano."

Whitney's vocal stylings have had a significant impact on the music industry. She has been called the "Queen of Pop" for her influence during the 1990s, commercially rivaling Celine Dion and Mariah Carey. Stephen Holden from The New York Times, in his review of Whitney's Radio City Music Hall concert on July 20, 1993, praised her attitude as a singer highly, writing "Whitney Houston is one of the few contemporary pop stars of whom it might be said: the voice suffices. While almost every performer whose albums sell in the millions calls upon an entertainer's bag of tricks, from telling jokes to dancing to circus pyrotechnics, Ms. Houston would rather just stand there and sing." He added the comments on her singing style: "Her [Whitney's] stylistic trademarks―shivery melismas that ripple up in the middle of a song, twirling embellishments at the ends of phrases that suggest an almost breathless exhilaration―infuse her interpretations with flashes of musical and emotional lightning." Elysa Gardner of Los Angeles Times in her review for The Preacher's Wife Soundtrack praised highly for Whitney's vocal ability, commenting "she is first and foremost a pop diva―at that, the best one we have. No other female pop star―not Mariah Carey, not Celine Dion, not Barbra Streisand―quite rivals Whitney in her exquisite vocal fluidity and purity of tone, and her ability to infuse a lyric with mesmerizing melodrama."