Unintentional weight loss is often a presenting symptom of upper gastrointestinal (UGI) cancer which progresses over the patients’ treatment journey and is a prognostic indicator of morbidity and mortality. The aim of this study was to investigate the effect of early and intensive dietetic counselling on quality of life in people with UGI cancer compared with usual care; and compare two modes of intervention delivery: telephone vs. an asynchronous mobile application (App). Eligible participants were those newly diagnosed with UGI cancer. Participants were randomised to one of three groups: intervention via telephone, intervention via an App, or usual care. The intervention was additional to usual dietetic care and delivered by a dietitian using standardised behaviour change techniques, individually tailored to participants, initiated within 4 weeks of diagnosis and continued for 18-weeks. The primary outcome was quality-adjusted life years (QALY) determined using the EQ-5D-5L quality of life assessment tool and secondary outcomes included weight and survival, assessed at three, six and twelve months. Data were analysed using linear mixed models. One hundred and eleven participants were randomised. QALY and survival were not significantly different between groups over the 12-month follow up. Participants receiving the intervention via telephone lost less weight compared with those in the mobile App group (adjusted coefficient 2.56 kg (95% CI 4.89, 0.23), p=0.031). The mobile App group had a greater number of withdrawals compared with the telephone group. Early and intensive dietetic counselling did not change QALY or survival during 12 months follow up compared with usual care. Nutrition counselling delivered via telephone, but not the mobile App, was effective for attenuating weight loss over the 12 months follow up.