Introduction: Smartphone addiction is a hotly debated public health issue and it affects every generation especially the youth and younger generation nowadays (Generation Z / i-Generation) and contributes to the poor mental health status like stress, anxiety and depression. This study is carried out to determine the prevalence of smartphone addic-tion and its association with stress, anxiety and depression among the undergraduate students in Unitversity Malaysia Sabah. Methods: A cross-sectional study was conducted among the undergraduate students in Universiti Malaysia Sabah. A total number of 456 undergraduate students in Universiti Malaysia Sabah with at least a smartphone device were enrolled in the study by stratified random sampling. A self-administered questionnaire, Smartphone Addiction Scale Malay Version (SAS-M) and The Depression, Anxiety and Stress Scale – 21 Items (DASS-21) Malay Version were used for data collection. The prevalence of smartphone addiction, stress, anxiety and depression among un-dergraduate students of Universiti Malaysia Sabah were determined. Simple linear regression was used to determine the effect of smartphone addiction to stress, anxiety and depression. Results: Prevalence of smartphone addiction among undergraduate students in Universiti Malaysia Sabah is 61.2% (95% CI : 56.5%, 65.7%). The prevalence of stress, anxiety and depression among undergraduate students in Universiti Malaysia Sabah are 34.9%, 58.6% and 42.5% respectively. The univariate analysis shows that smartphone addiction is significantly associated with stress (Regression Coeeficient = 0.774, 95% CI 0.54, 1.01 ; P-value