Deep neck infection (DNI) is a severe disease of the deep neck spaces, which has the potential for airway obstruction. Cervical necrotizing fasciitis (CNF) is a fatal infection of the diffuse soft tissues and fascia with a high mortality rate. This study investigated risk factors in patients with concurrent DNI and CNF. A total of 556 patients with DNI were included in this study between August 2016 and December 2021. Among these patients, 31 had concurrent DNI and CNF. The relevant clinical variables were assessed. In univariate analysis, age (> 60 years, odds ratio (OR) = 2.491, p = 0.014), C-reactive protein (CRP, OR = 1.007, p < 0.001), blood sugar (OR = 1.007, p < 0.001), and diabetes mellitus (DM, OR = 4.017, p < 0.001) were significant risk factors for concurrent DNI and CNF. In multivariate analysis, CRP (OR = 1.006, p < 0.001) and blood sugar (OR = 1.006, p = 0.002) were independent risk factors in patients with concurrent DNI and CNF. There were significant differences in the length of hospital stay and therapeutic management (intubation, tracheostomy, incision and drainage) between DNI patients with and without CNF (all p < 0.05). While there were no differences in pathogens between the DNI alone and concurrent DNI and CNF groups (all p > 0.05), the rate of specific pathogen non-growth from blood cultures was 16.95% (89/525) in the DNI alone group, in contrast to 0% (0/31) in the concurrent DNI and CNF group (p = 0.008). Higher CRP and blood sugar levels were independent risk factors for the concurrence of DNI and CNF. With regard to prognosis, there were significant differences in the length of hospital stay and therapeutic management between the groups with and without CNF. While there were no significant differences in pathogens (all p > 0.05), no cases in the concurrent DNI and CNF group showed specific pathogen non-growth, in contrast to 89/525 patients in the group with DNI alone.