Background: Contemporary health policy is shifting towards remotely delivered care. A growing need to provide effective and accessible services, with maximal population reach has stimulated demand for flexible and efficient service models. The implementation of evidence-based practice has been slow, leaving many services ill equipped to respond to requests for non-face-to-face delivery. To address this translation gap, and provide empirically derived evidence to support large-scale practice change, our study aimed to explore practitioners' perspectives of the factors that enhance the delivery of a NICE-recommended psychological intervention, i.e. guided self-help by telephone (GSH-T), in routine care. We used the Theoretical Domains Framework (TDF) to analyse our data, identify essential behaviour change processes and encourage the successful implementation of remote working in clinical practice. Method: Thirty-four psychological wellbeing practitioners (PWPs) from the UK NHS Improving Access to Psychological Therapies (IAPT) services were interviewed. Data were first analysed inductively, with codes cross-matched deductively to the TDF. Results: Analysis identified barriers to the delivery, engagement and implementation of GSH-T, within eight domains from the TDF: (i) Deficits in practitioner knowledge, (ii) Sub-optimal practitioner telephone skills, (iii) Practitioners' lack of beliefs in telephone capabilities and self-confidence, (iv) Practitioners' negative beliefs about consequences, (v) Negative emotions, (vi) Professional role expectations (vii) Negative social influences, and (viii) Challenges in the environmental context and resources. A degree of interdependence was observed between the TDF domains, such that improvements in one domain were often reported to confer secondary advantages in another.