OBJECTIVE: This study aimed to provide pharmacy educators with an understanding of threshold concepts as a framework that can help understand and support the internal work involved in professional identity formation (PIF). FINDINGS: Threshold concepts are transformative and troublesome concepts critical to the transition from trainee to practitioner. In particular, threshold concepts shed light on the individual, recursive, and transformational processes learners undertake while they grapple with important professional practices as they explore what it means to be a pharmacist. While there has been limited discussion in pharmacy education, health professions education literature has described threshold concepts related to ways of practicing and PIF. SUMMARY: Pharmacy educators can use the framework of threshold concepts to better understand the learner's developmental process (ie, their internal work, pathway, and trajectory) in coming to "think, act, and feel" like a pharmacist. Future work can further explore and define essential threshold concepts for pharmacy.