Therapist-guided internet-based cognitive behavioural therapy (iCBT) has improved access to treatment for depression and anxiety, but scalability is limited by reliance on trained therapists. This feasibility trial evaluated a tailored digital self-help intervention for adults with depressive and anxiety symptoms, delivered with or without clinician guidance. In total, 124 participants in Sweden with at least mild depressive or anxiety symptoms were recruited through social media and randomized (1:1) to an eight-week program with (n = 63) or without (n = 61) clinician guidance. All participants completed telephone assessments before and after the intervention. The primary aim was to assess feasibility of both versions, while considering outcome advantages of guidance and reduced clinician time with self-help. Feasibility outcomes included adherence, credibility, satisfaction, and adverse events. The intervention was perceived as credible, with high satisfaction and engagement: most participants used the program weekly, and two thirds completed at least three of five modules. Outcomes were similar across groups, though participants with guidance reported higher satisfaction. Clinician time averaged 36 minutes for self-help participants and 66 minutes for those receiving guidance. Both groups showed large symptom reductions (Cohen's d = 1.05-1.10), supporting feasibility and motivating future trials comparing self-help and clinician-guided delivery.