The number of people counting calories through apps is increasing, yet concerns have been raised that this could trigger symptoms of eating disorders. Although associations between calorie tracking and eating disorder symptomatology have been identified, further research is needed to understand motives for, and the perceived impact of, using a calorie tracking app. This study addressed these gaps with data collected from 1357 adults. A high percentage of participants (n = 964; 71%) had used a calorie tracking app; 531 participants (39%) reported currently using a calorie tracking app. Prior users reported higher levels of thinness- and muscularity-oriented disordered eating than non-users. Those using a calorie tracking app for weight-control/shape reasons were more likely to report that the app had contributed to several eating disorder symptoms (i.e., food preoccupation, all-or-none thinking around food, food anxiety, purging behaviours) than those using an app for health/disease prevention reasons. Engaging in a calorie tracking app for weight/shape reasons was associated with higher perceived helpfulness of calorie tracking app ratings and higher symptom severity. Findings suggest that underlying motives may be important to consider in research investigating the use of calorie tracking apps, as well as for health professionals working with clients engaging in these dietary monitoring tools.