Purpose: To evaluate how risk factors impact success rates of initial probing and nasolacrimal duct (NLD) tube intubation in children over 18 months of age with congenital nasolacrimal duct obstruction (CNLDO). Methods: This cohort study included 98 CNLDO patients aged 18 months to 10 years who underwent NLD probing with stent insertion. We employed the multivariate frailty model as our final model to conceptually elaborate on our correlated eye data, with the primary outcome measure evaluating the success rates of probing and tube intubation. Factors such as age, probing complexity, tube type, prior surgeries, and passive smoking were considered in the evaluation. Results: The study involved 98 patients (54 males, 44 females) with a mean age of 41.46 months and an average follow-up of 98.37 days (95 % CI 87.65–109.1). Out of the 110 eyes that underwent surgery, 13 (11.8 %) experienced failure while 97 (88.2 %) were censored. Kaplan-Meier analysis indicated significant differences in age category and probing (P-value = 0.03 and 0.006 respectively), but not tube type (P-value = 0.8). Multivariable analysis confirmed that older age and complex probing were associated with higher failure rates in CNLDO cases, with each monthly increase correlating to a two percent higher likelihood of intubation failure. Conclusions: Patient age and probing complexity influence CNLDO treatment, impacting surgical techniques and outcomes. Tube type, prior surgery, and passive smoking have no significant impact on treatment success.