Therapists with Integrative or Eclectic (I/E) theoretical orientations make up at least 30% of practitioners in the United States. Although several treatment selection models have been proposed and tested, little is known about the way I/E clinicians make decisions and choose among potential interventions in actual practice. Using a qualitative, collective, instrumental case study design, the current study explored how practicing I/E therapists make treatment selection decisions. Five licensed, currently practicing I/E psychologists consented to be interviewed individually during three audio taped meetings, using an in-depth-interviewing protocol. One participant withdrew after the first interview. Thus, four participants had complete data sets for Intra-case analyses: one man and three women, with 5-15 years of post-licensure experience, working in private practices, a university-affiliated counseling center, and an outpatient clinic. The fifth participant's partial data were included only in the final Cross-case analysis. Transcripts were first analyzed by the author and another researcher, and then further analyzed by the author alone. Intra-case analyses revealed nuanced accounts of each of the four therapist's approaches to treatment selection. Further, a Cross-case analysis yielded six Assertions: 1) Treatment decisions emerged from I/E orientations: What this orientation meant to therapists, why it was chosen, how it developed. 2) I/E therapists used stable theoretical or philosophical cores, plus ample flexibility to inform treatment. Participants reported similar core approaches: humanistic, relational, dynamic, or interpersonal. Flexibility was fundamental to I/E treatment selection. 3) The therapeutic relationship was inextricably linked to the treatment selection process, impacting it in complex and subtle ways. 4) Therapists' conflicted disavowal of Empirically Supported Treatments (ESTs) led them to feel like a silent majority. 5) Therapists based treatment selection on certain concrete, specific variables: timing, diagnosis, formal assessment, treatment goals, and larger sociopolitical contexts. However, these were less salient than other factors. 6) Therapists' treatment decision processes were experienced as primarily implicit. Based upon the results, a set of Working Hypotheses about I/E treatment selection processes were generated as directions for future research. Limitations are acknowledged, and implications for the research-practice gap, and for therapist training are discussed.