The current study aimed to identify the role of Mindulness in moderating the relationship between Smartphone Addiction and anxiety, depression, and sleep quality among university students, identifying the differences between high and low smartphone addiction in mindfulness, anxiety, depression, and sleep quality, finally identiying the relationship between smartphone addiction, mindfulness, anxiety, depression, and sleep quality.The sample consisted of 570 male and female students from the universities of Fayoum and Ain Shams of (229) males and (341) females, whose ages ranged from 18 to 25 years old with an average age of 19,87 years and a standard deviation of 2,50 years. The tools included: a questionnaire of data collection, Freiburg mindfulness inventory, prepared by (Walach et al.,2006), Smartphone Addiction Scale (Kwon et al., 2013), Generalized Anxiety Scale, Hopkins Symptom Checklist-25 (HSCL) depression scale (In: Fares et al., 2019), , and sleep quality scale prepared by Yi et al ( 2006), the study reached the following results : -There weren't statistically significant differences between male and female students in smartphone addiction, mindfulness, anxiety, depression and sleep quality, but there were differences between theoretical and emprical college students in smartphone addiction, mindfulness, and sleep, but there were no differences. Between them in anxiety and depression.-There were statistically significant differences between low and high smartphone addiction in mindfulness and sleep quality toward lowers in smartphone addiction, but the differences found in both anxiety and depression toward highers in smartphone addiction.-There was a negative relation at the level of 0.01 between smartphone addiction and mindfulness, and a negative statistically significant relation at 0.001 level between smartphone addiction and sleep quality, and in contrast, a positive statistically significant relation was found at the 0.001 level between smartphone addiction and anxiety and depression.-Mindfulness contributes in moderating the relationship between smartphone addiction, anxiety, depression, and sleep quality among the sample.