Background: There is an urgent need for psychosocial interventions that effectively support dementia caregivers in daily life. The Experience Sampling Methodology (ESM) offers the possibility to provide a more dynamic view of caregiver functioning. ESM-derived feedback may help to redirect caregivers' behavior towards situations that elicit positive emotions and to increase their feelings of competence in the caretaking process. This paper presents the design of a study that evaluates the process characteristics and effects of the ESM-based intervention 'Partner in Sight'. Methods/design: A randomized controlled trial with 90 spousal caregivers of people with dementia will be conducted. Participants will be randomly assigned to the experimental (6-week ESM intervention including feedback), pseudo-experimental (6-week ESM intervention without feedback), or control group (care as usual). Assessments will be performed pre- and post-intervention and at 2-, and 6-month follow-up. Main outcomes will be sense of competence, perceived control, momentary positive affect, and psychological complaints (depressive symptoms, perceived stress, anxiety, momentary negative affect). In addition to the effect evaluation, a process and economic evaluation will be conducted to investigate the credibility and generalizability of the intervention, and its cost-effectiveness. Discussion: The potential effects of the ESM intervention may help caregivers to endure their care responsibilities and prevent them from becoming overburdened. This is the first ESM intervention for caregivers of people with dementia. The results of this study, therefore, provide a valuable contribution to the growing knowledge on m-health interventions for dementia caregivers. Trial registration: Dutch Trial Register NTR4847 ; date registered Oct 9, 2014.