Usability evaluation is difficult to reconcile with agile software development for eHealth systems, because traditional usability evaluation is often complex and cumbersome to implement. However, obtaining prospective users' feedback during agile software development is crucial for improving the usability of eHealth systems, which is why there is an increasing need for agile eHealth usability evaluation. This study investigates whether agile usability evaluations are suitable to evaluate patient-centered eHealth systems being agile developed in health care and are applicable for prospective users, such as older persons suffering from age-related declines. A triangulation study was conducted combining iterative expert interviews with an exploratory case study. The triangulation study revealed that the implementation of an agile eHealth usability evaluation with prospective users such as older persons proved to be possible. Established eHealth usability evaluation methods must be further evolved to address age-related impairments of older persons.