Objectives: To examine the effects of web-based SUpport PRogram (SUPR) for communication partners (CPs) of persons with hearing loss (PHLs) in a HA dispensing setting. Design: Cluster randomised controlled trial (cRCT) with two arms (SUPR: Booklet, online videos; care as usual: no support) plus process evaluation. Measurements: baseline, and immediately-, six, and 12 months post-intervention. Outcomes: Significant Other Scale for Hearing Disability (SOS-HEAR), International Outcome Inventory for HAs/Alternative Interventions for Significant Others (IOI-HA/AI-SO). Process evaluation: dose-received, satisfaction, and benefit. Study sample: The cRCT included 73 (SUPR) and 57 (care as usual) CPs. In the process evaluation study, 41 CPs (SUPR) participated. Results: There were no significant effects of SUPR for third-party disability (SOS-HEAR), the proxy report (IOI-HA-SO item “use”), and third-party disability (IOI-HA-SO items “satisfaction”, and “quality of life”). SUPR-videos were watched by 15-22% of the CPs. SUPR materials were rated as moderately beneficial and useful. Conclusions: Low baseline disability (floor effect) and low intervention dose-received may explain the findings. Directly targeting CPs rather than via their PHLs and providing intervention materials specifically for CPs may improve their engagement and contribute to SUPR’s value supplementary to standard HA care.