A post-disco and funk song, "Wanna Be Startin' Somethin'" was viewed as a nod to the disco sound of Jackson's material on his previous studio album, Off the Wall, released in 1979. Arranged by Jackson himself and played by percussionist Paulinho da Costa, the song's rhythm was regarded as a "complex interweaving of drum-machine patterns and work", while the horn section, arranged by Jerry Hey, was described as both "brassy and precise". Slant Magazine commented that the song was a "complicated tapestry of colliding hooks and pop references." The song's lyrics, "Too high to get over, too low to get under", has strong similarities to Funkadelic's opening salvo for "One Nation Under a Groove".

The lyrics pertain to the media and press, as well as gossip and people trying to start arguments or problems for no reason, which he states in the lyrics, "Someone's always tryin' to start my baby crying," and then goes to a more "quasi paranoia" yield in the "near-bitterness" chorus, 'You're a vegetable, you're a vegetable/ You're just a buffet, you're a vegetable/ They'll eat off you, you're a vegetable.'" In "Wanna Be Startin' Somethin'", Jackson's vocal range spans from E3 to A5. The sheet music for the song shows four sharps with a suggested tempo of "moderately bright" in common time. It has a basic sequence of D/E–E–D/E–E as its chord progression, similar to that of “Don't Stop 'Til You Get Enough”. The coda at the end of the song - "Mama-say mama-sah ma-ma-coo-sah" - is a variant of a lyric in Cameroonian saxophonist Manu Dibango's 1972 disco song "Soul Makossa". Makossa is a Cameroonian music genre and dance. Dibango sued Jackson and, in 1986, settled out of court for one million French francs, agreeing thereby to waive future rights to this recording but not future use of the material.

Christopher Connelly, a writer for Rolling Stone, described "Wanna Be Startin' Somethin'" as being Thriller's "most combative track". Connelly noted that in the "hyperactive" song, Jackson's "emotions are so raw that the song nearly goes out of control". He further commented that the song has a "tune that's almost as exciting as seeing Jackson motivate himself across a concert stage – and a lot more unpredictable". Remarking that while the song's lyrics "won't keep Elvis Costello awake nights", they "do show that Jackson has progressed past the hey-let's-hustle sentiments that dominated Off the Wall". He added that Jackson's "raw ability and conviction make material like 'Baby Be Mine' and 'Wanna Be Startin' Somethin'' into first-class cuts". Cash Box called the song a "smash," specifically praising the "danceable groove...superb arrangement and strange but ultimately uplifting lyrics."

Stephen Thomas Erlewine, a writer for AllMusic, listed "Wanna Be Startin' Somethin'", along with "Beat It", "Billie Jean", and "Human Nature", as being the best songs from Thriller. He also described the song as the "freshest funk on the album". Eric Herderson, a writer for Slant Magazine, commented that with "three quick rimshots", he felt that "Wanna Be Startin' Somethin'" was like a "court fanfare". Robert Christgau, a music critic, commented that he'd "expect to bear more" of Thriller's "Wanna Be Startin' Something" and "Thriller" on the "dancefloor" rather than in his "living room". "Wanna Be Startin' Somethin'" received one Grammy Award nomination; it was nominated for "Best R&B Song" at the 1984 Grammy Awards, but lost to "Billie Jean," another of Jackson's singles from Thriller.

Pitchfork ranked this song No. 2 on its list of "The 200 Best Songs of the 1980s", writing that "if you're going to become the biggest star in the world, it helps to make the biggest song".

In 1983, "Wanna Be Startin' Somethin'" had a good chart performance worldwide. The song entered the Billboard Hot 100 chart top ten positions on July 2, 1983, at number nine, having moved up six places from the song's previous week. On July 16, "Wanna Be Startin' Somethin'" charted at number five, which was the song's peak position on the chart. The song's peak position made "Wanna Be Startin' Somethin'" Thriller's fourth consecutive single to peak within the top ten on the Billboard Hot 100. It was more commercially successful than Thriller's follow-up single "Human Nature" on the Billboard Hot 100, with the song peaking on the chart at number seven. The song also peaked within the top ten, at number five, on the Black Singles Chart.

Internationally, the song was commercially successful, mainly charting within the top 20 and top 30 on music charts. In the United Kingdom, on June 11, 1983, the song entered the chart's top 40 positions at number 38. The following week, the song moved up 24 positions to number 14, and on June 25, the song peaked within the top ten at number eight. The song remained on the charts for a total of nine weeks in 1983. In New Zealand, on July 24, 1983, "Wanna Be Startin' Somethin'" entered the charts at number 47. The following week, the song peaked at number 35, which was its peak position, and remained in the top 50 of the chart for three weeks. "Wanna Be Startin' Somethin'" entered the Dutch charts on July 9, 1983, charting within the top five at number four. The following week, the song charted at number three, which was its peak position, for three consecutive weeks. The song charted within the top ten for several weeks, and remained in the top 20 for ten weeks in 1983.

In 2008, after the release of Thriller 25 the song re-entered music charts worldwide. "Wanna Be Startin' Somethin'" entered the Italian music charts on February 21, 2008, charting at number 14; it remained on the chart for only one week. The song entered the Danish music charts on February 28, charting within the top 30 at number 29. The following week, it peaked at number 22. In Switzerland, the song entered the top 50 at number 47 on February 24, 2008. The following week, the song peaked at number 30. After a total of six weeks on the chart the song, fell out of the top 100, and after four weeks re-entered the chart at number 83, before falling off the chart again.

Following Jackson's death in June 2009, his music experienced a surge in popularity. "Wanna Be Startin' Somethin'" re-entered the United Kingdom charts on July 4, 2009, and peaked at number 57 the following week. On July 12, "Wanna Be Startin' Somethin'" re-entered Switzerland music charts for the second time. The song charted at number 37, which was its peak position, and remained on the charts for three weeks, before charting out of the top 100 positions.