BackgroundSmartphone addiction is exponentially increasing worldwide. It has negative health consequences. Previous systematic reviews identified several risk factors of smartphone addiction; however, they were based on cross‐sectional data. This systematic review aimed to fill the gap by assessing smartphone addiction risk factors using longitudinal studies.MethodsThis systematic review is registered with PROSPERO (CRD42023431529) and followed the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. Six databases, including Scopus, Medline, Web of Science, PubMed, ProQuest Central and PsycINFO, were searched to identify eligible studies. Studies were eligible if they assessed smartphone addiction as the outcome variable, were longitudinal and were published in English. All papers included in this review were assessed for the risk of bias and quality.ResultsA total of 22 papers met the inclusion and exclusion criteria after the screening process. The results were categorised into three groups, including personal, social and environmental factors. Within the groups, seven risk factors, including mental health, emotions, academic stress, social rejection and peer victimisation as well as family dysfunction and parental phubbing, were identified. All of the risk factors were significant predictors of smartphone addiction. Mental health problems, social rejection and peer victimisation also displayed a bidirectional relationship with smartphone addiction. Inconsistent smartphone addiction measurements were used.ConclusionThis review has significant implications for policymakers as it identified seven risk factors for smartphone addiction. Further studies are warranted to improve the understanding of the aetiology of smartphone addiction and inform education, counselling and coping with smartphone addiction.