Delay in time to treatment initiation (TTI) is associated with worsened survival outcomes in laryngeal squamous cell carcinoma (LSCC). It is unclear whether this is due to tumor growth or an increased risk of metastatic disease. This retrospective cohort study at one academic center included patients with LSCC who underwent radiotherapy/chemoradiotherapy between 2005 and 2017. We examined the association between tumor growth rate (TGR) and survival outcomes. Among 105 patients (mean age, 63.8 ± 11.1 years; 72% male), the threshold between "slow-growing" and "fast-growing" tumors was >0.036 mL/day (survival) and >0.082 mL/day (recurrence). Faster growth was associated with worse overall survival (OS) (hazard ratio, 1.97; 95% confidence interval [CI], 0.94-4.13) and increased recurrence (odds ratio, 9.10; 95% CI, 2.40-34.4). TGR >0.036 mL/day during TTI was associated with decreased OS, and >0.082 mL/day was associated with increased recurrence. Tumor measurement in patients experiencing delay may identify those who could benefit from escalated therapy.