Objective To investigate the status quo of illness uncertainty and role adaptation in mothers with babies in Neonatal Intensive Care Unit (NICU) and to explore the correlation between the two. Methods Totally 300 mothers with babies admitted in the NICU of 3 Class Ⅲ Grade A hospitals in Wenzhou between April and November 2017 were selected by convenient sampling. The demographic characteristics questionnaire for parents with babies in NICU, the Mishel Illness Uncertainty Scale for Parents and the Role Adaptation Questionnaire were used to investigate the mothers. The univariate analysis, Pearson correlation analysis and multiple stepwise regression analysis were employed to explore the influencing factors to their role adaptation. A total of 300 questionnaires were distributed, and 273 valid questionnaires were collected. Results The total score of the Mischel Illness Uncertainty Scale in the 273 mothers with babies in NICU was (98.58±11.78), and their score in role adaptation was (59.84±8.16). Illness uncertainty and role adaptation were negatively correlated in the mothers with babies in NICU (r=-0.230, P＜0.05). According to the multiple stepwise regression analysis, complexity and information famine in illness uncertainty of mothers were the influencing factors to the mothers' role adaptation. Conclusions The level of role adaptation in mothers with babies in NICU is low, and their illness uncertainty may be used to predict their role adaptation. NICU nursing staff should take targeted measures to reduce the mothers' illness uncertainty and improve their role adaptation.