Objective: To investigate the role of NF-kappa B in regulating myosin heavy chain (MyHC) content and muscle atrophy following laryngeal muscle denervation. Methods: Rats were divided into five groups: (1) recurrent laryngeal nerve injury (RLNI), (2) RLNI with NF-kappa B inhibition, (3) sham operation, (4) sham operation with injection, and (5) blank control. MyHC content and muscle atrophy in the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were assessed over 14 days post-operation. Results: In the RLNI group, MyHC levels in TA muscle decreased progressively, with significant atrophy observed after 7 days. NF-kappa B inhibition delayed MyHC reduction until Day 11 and temporarily mitigated atrophy, though these effects diminished over time. In PCA muscle, MyHC levels showed a biphasic pattern, decreasing at Day 3, increasing on Days 7 and 11, and declining again by Day 14. PCA muscle atrophy progressed gradually, stabilizing by Day 11. NF-kappa B inhibition in PCA muscle led to delayed and less severe atrophy compared to the RLNI group, with higher MyHC levels observed on Days 3 and 7 but lower levels on Days 11 and 14. Conclusions: Within 14 days of denervation, the extent and timing of MyHC decline and muscle atrophy differ between TA muscle and PCA muscle. PCA muscle exhibits earlier changes than TA muscle. NF-kappa B inhibition temporarily delays muscle atrophy and MyHC loss but cannot sustain these effects long-term.