This research applied a mixed-approach method to investigate Smartphone usage, gratifications, and addiction among SQU undergraduates, adopting the uses and gratifications theory (UGT) as a framework and the DNA wheel measurement as an analysis technique. Furthermore, the study aimed to explore the role of gender, field of study, academic achievement, parents' education, and family income on Smartphone usage, gratifications and addiction. This research also aimed to examine relationship between Smartphone usage, gratifications and addiction. Two questionnaires on Smartphone usage, gratifications, and addiction had been applied to a stratified sample comprising (849) undergraduate students at SQU (48.8% male, 51.2% female). In addition, the researcher conducted four discussion sessions with two focus groups to support the quantitative data collected through the questionnaires. The quantitative findings indicated that WhatsApp/text message services were the heaviest Smartphone applications usage. Voluntary usage behavior was the most common type of Smartphone usage behavior, while seeking information and entertainment were the most common Smartphone gratifications among SQU undergraduates. The prevalent rate of Smartphone addiction was 33.1%, while disregard of harmful consequences was the most frequent addiction symptom among those students. The finding also revealed significant differences at (p< 0.05) in Smartphone usage, gratifications, and addiction related to: Gender, field of study, parents' education level, and family income level. According to student's academic achievement there were significant differences at (p<0.05) in Smartphone addiction, while there were no significant differences at (p<0.05) in terms of Smartphone usage and gratifications between SQU undergraduates. The qualitative findings not only highlighted the reasons behind Smartphone, usage, gratifications, and addiction among SQU undergraduates but also explained relationships between Smartphone usage, gratifications, and addiction among those students with some demographic factors. In addition, the research findings explained the relationship between Smartphones addiction, usage and gratification. Finally, this study proposed some solutions to the problem of Smartphone addiction among those students. Key words: Smartphone usage, Smartphone gratifications, Smartphone addiction, Uses and Gratifications Theory, DNA wheel measurement, Sultan Qaboos University Undergraduates, Oman.