Purpose: Ultrasound-guided regional anesthesia (UGRA) is an essential skill in anesthesiology, yet non-regional anesthesia fellowship-trained anesthesiologists often have limited opportunities to perform it. Using the Theoretical Domains Framework(TDF), we aimed to explore the barriers to and facilitators of anesthesiologists' performing UGRA without fellowship training in Canada.

Methods: We conducted a qualitative study following ethics approval, using semistructured interviews with 15 Canadian staff anesthesiologists who did not complete a regional anesthesia fellowship. Interviews were audio-recorded, transcribed, and analyzed using NVivo 12 (QSR International, Burlington, MA, USA) with a deductive coding approach based on the TDF. We used predefined criteria to identify relevant TDF domains that influence the performance of ultrasound-guided regional anesthesia.

Results: We achieved data saturation by the 15^th interview. Eight TDFdomains were identified as most relevant to performing UGRA. Key facilitators were institutional support and dedicated resources, training and practice opportunities, mentorship and teamwork, and confidence. Major barriers were lack of resources/staff/time, surgeon resistance, fear of complications/workflow disruption and provider anxiety, low confidence, and insufficient training/practice.

Conclusions: Ultrasound-guided regional anesthesia adoption by non-regional anesthesia fellowship-trained anesthesiologists is influenced by a complex interplay of individual, social, and environmental factors. These findings highlight clear targets for implementation strategies, including more training, resource allocation, and strengthened interdisciplinary collaboration across departments such as anesthesia, surgery, and emergency medicine. Addressing these barriers and leveraging enablers through theory-informed interventions may increase UGRA uptake and ultimately lead to better perioperative patient care.