Objective The objective of this study was to determine the diagnostic value of quantitative border irregularity assessment and apparent diffusion coefficient (ADC) in patients with squamous cell carcinoma of the tongue (SCCT). Methods Cervical lymph nodes (n = 192) from 63 patients with SCCT were examined preoperatively by magnetic resonance imaging, including routine head and neck sequences, dynamic contrast-enhanced magnetic resonance imaging, diffusion-weighted imaging, ADC, surface regularity (S-R), and visually assessed variables, and evaluated pathologically after surgery. Results Necrosis, lymphatic hilum, unclear margin, higher S-R,S- long to short axis ratio, and ADC were associated with metastasis in cervical lymph nodes (M-cLNs) and extranodal extension (ENE), and thickened nodal rim with ENE alone. Apparent diffusion coefficient, S-R, unclear margin, and visible necrosis were strongly associated with M-cLN, whereas S-R, unclear margin, and visible necrosis were associated with ENE status on logistic regression analysis. Conclusions Quantitative S-R and ADC data greatly improved diagnosis of M-cLNs and ENE, relative to visible variables alone in patients with SCCT.