Cross-national research using data from the Health Behavior in School-aged Children (HBSC) survey showed an increase in the prevalence of chronic back pain from 2002 to 2014. However, it is unknown if this trend has persisted beyond 2014. The aims of this study were to: (1) determine if the prevalence of chronic back pain in girls and boys aged 11, 13, and 15 continued to increase from 2014 to 2018; and if this was the case, to (2) examine whether this increase in the prevalence of chronic back pain between 2002 and 2018 was explained indirectly by increases in sleep difficulties and in psychological symptoms. Data from 789,596 adolescents retrieved from five waves of the HBSC survey conducted in 2002, 2006, 2010, 2014, and 2018 in 32 countries/regions were used. Logistic regressions and path analyses were conducted. Results showed an overall increase of 0.5% in the prevalence of chronic back pain between 2014 and 2018, ranging from 0.4% for 15-year-old girls to 1.3% for 11-year-old boys, indicating a continued overall increase in chronic back pain in adolescents beyond 2014. For 13-year-old girls and for 15-year-old girls and boys, the increase in the prevalence of chronic back pain between 2002 and 2018 was partially mediated by increases in sleep difficulties which in turn were associated with increases in psychological symptoms. The findings provide important information that may aid stakeholders enhancing public health initiatives to prevent or reduce the increasing trend in the prevalence of chronic back pain in adolescents. PERSPECTIVE: This study shows that chronic back pain prevalence continues to increase among adolescents, with sleep difficulties and psychological symptoms contributing significantly to this trend. The findings provide insights that may inform strategies to prevent or reduce the increasing trend of chronic back pain in adolescents.