This empirical study investigates attitudes about smart phones and their use by senior citizens in the Kingdom of Saudi Arabia (KSA), and develops general design guidelines for a smart phone interface designed to appeal to this group and thus increase the adoption of smart phones among its members. The overall rationale for the study is to enable seniors in Arabic-speaking, predominantly Muslim countries to better access the proven benefits of smart phone use among seniors, including positive impacts on mental functioning, the adoption of healthier lifestyles through improved access to healthcare information and applications, and to support more autonomous and independent living. Many studies have generated best practice guidance on smart phone design for seniors, but these have mostly been conducted in Western, English-speaking countries. This research builds on existing best practice guidance but uses the study findings to prioritize the most important design points relating to the needs of Arabic-speaking users in Muslim countries, and to identify any required additions or modifications to the existing guidance and to current theories of technology adoption. The initial findings of a survey of Saudi Arabian senior citizens were used to develop a prototype smart phone interface, which was evaluated by a sample of participants. The outcomes of this trial and the findings of semi-structured interviews were then used to develop final recommendations for a smart phone application for use by the target population, and for a modified theory of technology adoption.