By developing a software tool that helps students cultivate the habit of smiling, this study aims to enhance students’ interpersonal relationships and ability to interact with others and therefore effectively decrease their Internet addiction. The study participants were students from a vocational high school in Tainan, Taiwan. To begin with, it examined the choices of attachment styles and levels of Internet addiction among high school students enrolled in a practical skills program. The students used the software tool for fourteen consecutive days and completed their smile task, which was followed by a post-test questionnaire. The result shows that for interpersonal interactions, changes in the mean values for three types of attachment styles decrease (namely anxious–preoccupied, dismissive–avoidant, and fearful–avoidant styles). In particular, the dismissive–avoidant style was reported with the most prominent change of −1.267, and it was the only variable with a higher average value. This study also applied Bartholomew and Horowitz’s two-dimensional internal working model and found that the participants had demonstrated positive developments in their own self-internal modes and, in particular, others’ internal modes.