BACKGROUND: Mood episodes and high suicide risk of bipolar disorder (BD) are thought to derive from amygdala-ventral prefrontal cortex emotion regulation brain circuitry dysfunction and resulting emotion dysregulation, making these potential intervention targets. OBJECTIVE: To assess feasibility, acceptability, and preliminary efficacy in engaging the emotion regulation targets of two Brain Emotion Circuitry-targeted Self-Monitoring and Regulation Therapy (BE-SMART) variations in adolescents and young adults with BD (BD METHODS: In a single-blind, parallel, pilot-randomised trial, 60 BD FINDINGS: In addition to demonstrating feasibility, only BE-SMART-DR showed pre-treatment to post-treatment improvements in DR regularity (Cohen's CONCLUSIONS: Regularising DRs may enhance emotion regulation brain circuitry functioning, emotion regulation, and reduce suicide risk in BD CLINICAL IMPLICATIONS: Chronotherapeutic interventions regularising DRs, such as SRT, should be studied further as potential treatment strategies for BD TRIAL REGISTRATION NUMBER: NCT03183388.