Context: People who experience homelessness can face overwhelming challenges trying to access resources and services such as shelter, meals, and healthcare in urban areas. For primary healthcare and service providers who are caring for those who are homeless, it can be difficult connecting clients and patients with other agencies, describing the service, explaining how to get there, and days or times when the service is available. The Cincinnati Homeless and Community Resource Map is intended to provide access to meaningful resources and agencies. Objective: This study aimed to test the usability of a mobile phone app of community resources for persons who have experienced homelessness or other social determinants of health, service providers and primary healthcare providers. Study Design: Mixed-Methods study: Descriptive statistics will be used for scale and close-ended survey responses. Interview and open-ended survey data will be coded; themes will be derived using a thematic analysis approach. Setting: Urban community-based research. Population studied: Study participants include adults who are or have experienced homelessness and/or other social determinants of health, service providers, and primary healthcare providers. Intervention/Instrument: Study participants completed a Think Aloud protocol, semi-structured interview, System Usability Scale (SUS), and demographics survey in an in-person or remote meeting. An independent evaluation was also offered for service providers and primary healthcare providers to explore the app on their own and complete survey questions. Outcome Measures: SUS measures, interview transcripts and open-ended aggregate data will be coded to test useful content, current usability, and inform improvements to the app. Results: In progress. To date, a total of 34 individuals have evaluated the mobile phone app including 13 community members who are/or have experienced homelessness or other social determinants of health, nine service providers and 12 healthcare providers. Initial analysis highlights that 97% (33/34) of participants would use the app again. The average SUS is 82, earning an adjective rating of Excellent and letter grade A. Further results will contribute to understanding barriers of use and suggestions for improvements, as well as brand recognition of the mobile phone app for the end users.