Abstract: Tool use promotes tool embodiment and extends human body representation. Based on previous studies about tool embodiment, we aimed to explore whether smartphones could be integrated into body schema and extend body representation. We adapted the stimulus–response compatibility paradigm (Experiment 1a, n = 39; Experiment 1b, n = 44), the hand mental rotation paradigm (Experiment 2, n = 39; Experiment 3, n = 40), and the forearm bisection paradigm (Experiment 4, n = 40). The results revealed that participants showed a processing advantage for the picture of a smartphone held, indicating that smartphones could be integrated into the body schema. Moreover, the results showed that the perceived forearm length increased after imagining using a smartphone, indicating the extended body representation. Besides, we found no significant difference between high-frequency smartphone users and low-frequency smartphone users across the four experiments. These results underscored the unique role of smartphones in modifying the body schema and extending body representation, which was more potent than traditional tools and non-smartphones. Our findings provide empirical evidence for extended-self theory applied to smartphones and provide a novel insight into the impact of smartphone use on humans from the perspective of tool embodiment.