"Sittin' Up in My Room" was written and produced by Kenneth "Babyface" Edmonds. Edmonds also helmed the drum programming, synthesizer, and wurlitzer sounds, while Michael Thompson played the guitar."Bassy" Bob Brockmann mixed the track; recording was overseen by Brad Gilderman. The record was from a number of songs Edmonds specifically penned for the soundtrack of Forest Whitaker's 1995 romantic drama film Waiting to Exhale, starring Whitney Houston and Angela Bassett. Musically, songs from fellow R&B singer Aaliyah's debut album Age Ain't Nothing but a Number (1994) served as an inspiration while starting the song idea for "Sittin' Up in My Room". Edmonds finished most of the demo on his Los Angeles house, before Norwood came over for recording. Commenting on the recording process, Norwood later elaborated: “I was going crazy with my vocal runs because I really wanted to impress Babyface. I knew how to pull back, but it was one of those things where I thought, ‘This is my chance!’ I always wanted to work with Babyface going back to ["Tender Lover"] [...] Actually, he was the most legendary producer that I had worked with to that point. So when I was recording ‘Sittin’ Up In My Room,’ I was thinking, ‘This is my chance to show Babyface that I could sing!’ But he was like, ‘You don’t have to do all of that. Just sing, baby. Just keep your vocals simple.’”
Cheo Hodari Coker from the Los Angeles Times praised Babyface for his production on the song, stating "Babyface's funky-but-restrained background track is the real star of this jam. Using a pleasant mixture of plunking bass and synthesizer chords, [the song] proves that he has a grabbag of styles at his disposal." Craig Lytle from Allmusic wrote that "with a Sly Stone twist, Babyface concocts a laid-back funk groove for "Sittin' up in My Room," which features the humble vocals of Brandy. Though the song does not allow her to unwind with her higher notes, it does, however, reveal her lower octaves." In 2014, Complex magazine ranked the single 39th on its list of the 50 R&B Songs of the 1990s.
Released as the second single from the soundtrack, "Sittin' Up in My Room" debuted at number forty-six and number thirteen, on the Hot 100 Singles chart and Hot R&B Singles chart, the issue date of December 30, 1995, respectively. The single reached the number two on the Hot R&B Singles chart, the issue of February 17, 1996 and stayed there three consecutive weeks. It also peaked at number two on the Hot 100 Singles chart (kept from the top spot by Mariah Carey's One Sweet Day), staying on the chart for a total of thirty-three weeks. The single earned a platinum award by the Recording Industry Association of America (RIAA) on May 23, 1996, with 1,000,000 copies sold.
Waiting to Exhale actor Faison appears in the video.
The music video for "Sittin' Up in My Room" was directed by Hype Williams. Norwood declared filming as "fun" as she had a "great relationship" with Williams at that time, having previously worked with him on the videos for the Hip–Hop Remix of "I Wanna Be Down" and her second single "Baby". Actor Donald Faison appears in the video; Faison played the son of Loretta Devine's character Gloria in Waiting to Exhale. Commenting on the result, Norwood remarked: "It was a a great video, dance and everything. It was dope.”