Abstract Background Low and middle-income countries have growing older populations and could benefit from the use of multi-domain geriatric assessments in overcoming the challenge of providing quality health services to older persons. This paper reports on the outcomes of a study carried out in Cape Town, South Africa on the validity of the interRAI Check-Up Self-Report instrument, a multi-domain assessment instrument designed to screen older persons in primary health settings. This is the first criterion validity study of the instrument. The instrument is designed to identify specific health problems and needs, including psychosocial or cognition problems and issues related to functional decline. The interRAI Check-Up Self-Report is designed to be compatible with the clinician administered instruments in the interRAI suite of assessments, but the validity of the instrument against clinician ratings has not yet been established. We therefore sought to establish whether community health workers, rather than trained healthcare professionals could reliably administer the self-report instrument to older persons. Methods We evaluated the criterion validity of the self-report instrument through comparison to assessments completed by a clinician assessor. A total of 112 participants, aged 60 or older were recruited from 7 seniors clubs in Khayelitsha, Cape Town. Each participant was assessed by one of two previously untrained, non-healthcare personnel using the Check-Up Self-report version and again by a trained assessor using the clinician version of the interRAI Check-Up within 48 h. Our analyses focused on the degree of agreement between the self-reported and clinician-rated versions of the Check-Up based on the simple or weighted kappa values for the two types of ratings. Binary variables used simple kappas, and ordinal variables with three or more levels were examined using weighted kappas with Fleiss-Cohen weights. Results Based on Cohen’s Kappa values, we were able to establish that high levels of agreement existed between clinical assessors and lay interviewers, indicating that the instrument can be validly administered by community health workers without formal healthcare training. 13% of items had kappa values ranging between 0.10 and 0.39; 51% of items had kappa values between 0.4 and 0.69; and 36% of items had values of between 0.70 and 1.00. Conclusion Our findings indicate that there is potential for the Check-Up Self-Report instrument to be implemented in under-resourced health systems such as South Africa’s.