《One Thing》的詞曲創作和演唱都是由One Direction完成的。以下是《One Thing》的部分歌詞：
女：
Baby you know what I like
About your style and the way you do it
And I ain't gonna deny
That I'm a girl who likes what she likes
男：
And I don't give a damn about what they say
I'm in this with you til the end of the day
I'm all about one thing and that's making you mine
女：
So take a look at what we've got
And don't it make your heart beat faster?
Baby just let it show, oh
男：
Yeah, I don't give a second to think
It's now or never, I'm coming to the end
And I ain't got nothing left to pretend
女： One thing.
男：
And I ain't got nothing left to prove
So why bother try to prove it to you?
Come with me, there's no better place to be.
女：
Just let it be
男：
Oh oh oh oh 女： Oh oh oh 男：Oh oh oh oh 女：I want you all over me like a book without any covers. 男： I need to get with you now before they close the door. 女：You got me looking for a way to explain. 男：You know I want you, so why can't we just say it out loud? 女：One thing. 男：Yeah. 女：Oh oh oh oh. 男：Now I ain't gonna waste no time. 女：Oh oh oh oh. 男：I ain't gonna wait too long. 女：One thing. 男：Yeah. 女：Oh oh oh oh. 男：I ain't got nothing left to prove. 合唱：So why bother try to prove it to you? 女：Come with me, there's no better place to be. 合唱: Let me be your one thing, your one thing, your one thing, your one thing. （以上歌詞翻譯可能存在誤差，請以原版歌詞為準）