The mathematical concept of function is an essential underpinning for advanced study in mathematics, such as calculus, and influences success in higher mathematics. Teaching about functions is challenging as many students find it difficult to understand. Effective teaching strategies are reliant on a teacher’s knowledge of the current understandings of their students. The gestures of the twenty-three middle-secondary Australian students (14–15 years old) in this study clarified the meaning of their words as they were interviewed whilst viewing two different computer simulations. Five ways in which students used their hands when providing multiple representations of mathematical functions are presented, which provide insights into students’ thinking about functions not available in their words alone. Keywords: gesture, mathematics learning, functions, secondary school