This study aimed to investigate the level of a relatively new phenomenon, fear of missing out or FoMO, demonstrated by smartphone use during lectures among 2084 undergraduate students at Kuwait University. Fear of missing out describes the situation where a student cannot resist using their smartphone during lectures because of their desire not to miss anything that is happening, especially on social media. The study also sought to investigate whether fear of missing out was a predictor for attention distraction and learning disengagement among the students. It used a descriptive survey involving three scales: an attention distraction scale, a learning disengagement scale, and a fear of missing out scale. The level of fear of missing out among students was high and was strongly correlated with both attention distraction and learning disengagement. No significant correlation was found between fear of missing out and students' academic background. These results suggest some practical policies for higher education faculty members to use to lessen the negative outcomes of smartphone use and promote responsible use of smartphones in the classroom.