Background: Nomophobia can be defined as a disorder in which people fear being away from their smartphone. Studies on the determinants of nomophobia in young adults seem to be limited. Aim: This study aims to determine the levels of nomophobia, social appearance anxiety and loneliness in young adults and to examine the effects of social appearance anxiety and the level of social and emotional loneliness on nomophobia levels. Design: This is a descriptive and correlational study. Data were collected from 687 young adults. Data were collected using the Information Form, the Nomophobia Scale, the Social Appearance Anxiety Scale, and the Social and Emotional Loneliness Scale for Adults. Descriptive and multiple linear regression statistics were used. Results: The mean Nomophobia Scale score of the participants was 73.76 ± 27.46, which points to moderate nomophobia levels. The findings revealed those with a high level of social appearance anxiety have higher nomophobia levels. It was revealed that social appearance anxiety, social and emotional loneliness explain 8 % (Adjusted R2 = 0.082) of the variance in the nomophobia. Conclusion: A sample of 687 participants showed that young adults were relatively moderately nomophobic. In this study, social appearance anxiety, social and emotional loneliness was determined as predictor of nomophobia.