SummaryThe aim of this study was to evaluate the safety and efficacy of digital therapeutic application of Sleep Index‐Based Treatment for Insomnia (dSIBT‐I) and compare them with those of digital application of Cognitive Behavioural Therapy for Insomnia (dCBT‐I). This randomised prospective pilot study was conducted at the Asan Medical Center. A total of 50 patients with insomnia were recruited between December 2022 and January 2023 and randomly allocated to the dSIBT‐I or dCBT‐I group. The study was carried out for one month. The primary outcome was the significant reduction in Insomnia Severity Index score at Week 4 compared to baseline, while the secondary outcome was proportion of participants whose Insomnia Severity Index scores were reduced to <15 at Week 4. We performed linear mixed model and generalised estimating equation analyses. Both dSIBT‐I and dCBT‐I groups showed significant improvements in Insomnia Severity Index scores at Week 4. There was no significant difference between two groups in terms of Insomnia Severity Index scores at Week 4 (group × time effect, F = 1.07, p = 0.382) and proportion of participants whose Insomnia Severity Index scores were reduced to <15 at Week 4 (group × time effects, F = 1.80, p = 0.615). However, at Week 2, the dSIBT‐I group showed better results than the dCBT‐I group in terms of both Insomnia Severity Index scores (p = 0.044) and proportion of participants whose Insomnia Severity Index scores were reduced to <15 (82.6% vs. 48.0%, p = 0.017). No treatment‐emergent adverse events were reported in either group. The dSIBT‐I is a safe and effective therapy for insomnia, with rapid treatment effects.