Say You'll Be There is a mid-tempo dance-pop song, with influences of funk and R&B. It is written in the key of D♭major, with a time signature set on common time, and moves at a moderate tempo of 108 beats per minute. The song is constructed in a verse-chorus form. It uses the sequence B♭m–E♭–G♭m–D♭as its chord progression during the verses and the chorus. The third verse includes an instrumental solo, that closes with a coda, which consists in the group singing the chorus repeatedly until the song gradually fades out, while Melanie Chisholm adds the high harmony. Absolute played the instruments, except the harmonica, which was played by Judd Lander, who also played it on Culture Club's Karma Chameleon.
The lyrics, according to Brown are about relationships, and to be there for each other. That it does not matter to say that you love them, the only thing that they care is that their lover give his promise that he will be there for them whenever they need him. In Say You'll Be There, the group exuded a brash confidence that was attractive to their teenage fans. The Spice Girls decide to be friends, not lovers, the clear message is that the relationship can be channelled and controlled by the girl, with an emphasis on stating where they come from and what they stand for. The semi-R&B groove song, according to Melanie Brown depicts about the group telling that it does not matter to say that you love them, the only thing that they care is that their lover give his promise that he will be there for them whenever they need him.