This study explored concussion assessment and management self-efficacy and practices of allied healthcare professionals in Ireland. (1) Self-efficacy levels and practices vary across different concussion assessment and management skills, (2) the ability to practice skills impacts self-efficacy most. Cross-sectional. Level 3. Survey of allied healthcare professionals (285 responders), investigating (1) demographics, (2) concussion assessment (immediate and office) and management (postconcussion advice and management/rehabilitation) self-efficacy levels and practices, and (3) factors affecting self-efficacy. Levels of self-efficacy among clinicians were 64.5 ± 26.6 (immediate assessment) and 56.6 ± 25.4 (postconcussion advice) (highest scores: concussion symptom checklist [80 ± 28.4], physical rest advice [80.1 ± 27.8]; lowest: Child Sport Concussion Assessment Tool [44.6 ± 41.2] and nutrition advice [34.1 ± 33.7]). Overall levels of self-efficacy among Certified Athletic Therapists and Chartered Physiotherapists were 51.5 ± 20.1 (assessment) and 62.1 ± 20.9 (management) (highest scores: history/clinical evaluation nonspecific to concussion [86.6 ± 16.2], physical rest advice [86.3 ± 20]; lowest: paper/pencil neuropsychological test [16.7 ± 28.6], advice on medication use [39.2 ± 35]). A strong positive correlation was observed between clinician self-efficacy and frequency of use of overall (r = 0.795; P < 0.01) and immediate (r = 0.728; P < 0.01) assessment, advice (r = 0.805; P < 0.01), and management (r = 0.812; P < 0.01) skills. Factors with greatest positive impact on clinician self-efficacy were the ability to practice skills during clinical placement (3.3 ± 0.9) and remaining emotionally (3.3 ± 0.8) and physically (3.3 ± 0.8) calm while practicing. Clinicians in Ireland had moderate self-efficacy in concussion care. Those who used concussion-relevant skills frequently in practice displayed higher self-efficacy for those skills. Concussion-related self-efficacy can be enhanced through practice in a clinical environment and through experiencing composure while practicing.