Background/Objectives: In March 2024, a resident doctor’s strike in South Korea created staffing gaps in teaching-hospital emergency departments. The purpose of this study was to evaluate pre- and post-strike changes in job stress, self-efficacy, job satisfaction, and job performance confidence among paramedics who work in hospitals and to compare patterns of change by career stage. Methods: Paramedics who work in hospitals designated as regional and local emergency medical centers completed a structured 41-item questionnaire across four domains on a 5-point Likert scale. Retrospective pre- and post-strike ratings were analyzed using paired t-tests. Subgroup analyses compared senior (≥5 years) and junior (1–2 years) paramedics. Results: Job stress increased after the strike, including additional task instruction (2.8 ± 0.9 to 3.6 ± 1.0), insufficient rest (3.1 ± 0.7 to 3.9 ± 0.9), and multitasking burden (3.3 ± 0.8 to 4.1 ± 0.9). Self-efficacy declined modestly (confronting difficult tasks: 3.9 ± 0.9 to 3.6 ± 0.9). Job satisfaction decreased (reward after work: 3.9 ± 0.7 to 3.5 ± 0.9), while turnover intention increased (2.7 ± 1.0 to 3.9 ± 0.9). Performance confidence showed minimal change (competence: 4.4 ± 0.6 to 4.3 ± 0.8). Subgroup findings were similar in seniors and juniors, with stress increasing and self-efficacy decreasing overall. Conclusions: Resident workforce shortages increased job stress among paramedics working in teaching-hospital emergency departments and heightened negative perceptions of their work. To prepare for similar workforce crises in the future, it is necessary to revise and realign the legal scope of practice to reflect paramedics’ roles and responsibilities in real-world settings while simultaneously establishing the policy and institutional infrastructure needed to support these changes.