"I Think He Knows" chronicles the early days of Swift and Alwyn's relationship and how she quickly fell head over heels for him. Rhythmically, the song is also reminiscent of "King of My Heart." Swift sings, "He got that boyish look that I like in a man," which is not only a fairly accurate description of what Alwyn looks like but also another reference to how much younger he is than her recent exes.