Objective: The Relational Depth Frequency Scale (RDFS) was developed to measure the frequency of specific moments of profound contact and engagement in psychotherapy. Method: Following an initial process of item generation and rating, Three-Step Test Interviews were conducted with eight therapists and clients to further refine potential items. Sixteen relational depth items were then taken forward for psychometric assessment in an online sample of 336 therapists and 220 clients, each divided into separate “shortening” and “checking” subsamples. Results: Following psychometric scale shortening involving confirmatory factor analysis (CFA) and Rasch analysis, we formed a six item RDFS that could be used with both therapists and clients. The parameters of the shortened form replicated well in the independent checking subsamples with good internal consistency (Cronbach’s α = .85 and .93 in therapist and clients respectively), acceptable fit statistics in CFA and Rasch analysis, and moderate to high levels of convergent validity against the Working Alliance Inventory (Short Form, Revised) and Relational Depth Inventory (RDI-R2). Conclusion: As a brief self-report measure, the RDFS can be used to further assess the relationship between relational depth and therapeutic outcomes. Further research is needed to examine the reliability, validity, and acceptability of the RDFS in ongoing therapies in clinical settings.