BACKGROUND: There is little information available to inform the cost-effectiveness of eHealth interventions in improving patient health outcomes. A trial-based economic evaluation was undertaken in order to inform feasibility of conducting a mobile phone text messaging program targeting dietary behaviours in people receiving haemodialysis. METHODS: A trial-based economic evaluation from a health system perspective of a 6 month pilot randomised controlled trial was undertaken. 130 patients receiving haemodialysis from six dialysis units across Sydney, Australia were enrolled into the KIDNEYTEXT study. Usual care (inperson dietary counselling) was compared to usual care plus 3 semi-personalised dietary mobile phone text messages per week over a 6 month period. The outcomes of this economic evaluation included: cost of intervention, cost-effectiveness and marginal effects on total costs. RESULTS: The cost of developing and maintaining the KIDNEYTEXT intervention was US$110 per participant. Total costs were US$1418 higher in the usual care arm compared to the intervention arm. The incremental benefits for QALYs were 0.01 (95% CI -0.03 to 0.06) and dietary adherence (i.e. adherent to 3 or more dietary guidelines at 6 months) being 0.04 (95% CI -0.15 to 0.24). The largest component of total costs was related to unplanned admissions to hospital. CONCLUSIONS: Mobile phone text messages targeting dietary behaviours may be cost saving, while maintaining similar or improved dietary behaviours. A larger trial with longer follow-up time is warranted. This article is protected by copyright. All rights reserved.