Background: The crisis caused by the child's illness and hospitalization affects all family members. Fear, worry, and anxiety are common issues of hospitalized children’s mothers. Betty Newman's system model plays a vital role in adapting to stress detection and control. Objectives: This study aimed to examine the effect of the behavioral systems model on the concerns of mothers of children admitted to the surgical ward. Methods: This quasi-experimental study was conducted on 60 mothers of children admitted to the surgical ward of the Mousavi Hospital, Gorgan, Iran, in 2020. The participants were selected using convenience sampling and then divided into test and control groups using non-probability sampling. According to Neuman's systems model, participants in the test group received nursing care in 3 - 4 sessions (each lasting 30 - 45 minutes). Participants in the control group received only routine ward care. Data were collected using the Parental Concern Scale and analyzed with IBM SPSS Statistics 21 software using statistical tests (analysis of covariance, unpaired samples t-test, and paired sample test). Results: The mean score of maternal concerns before the intervention was 42.6 ± 3.06 in the control group and 43.21 ± 2.27 in the test group. The results of the independent samples t-test did not show any significant difference between the groups in terms of maternal concerns (P = 0.11). The mean post-intervention maternal concern score was 37.6 ± 2.71 and 41.716 ± 2.55 in the test and control groups, showing a significant difference between the groups as indicated by the t-test results (P < 0.01). However, the paired t-test outcomes showed no difference in the mean maternal concern score in the control group before and after the intervention (P = 0.92). In contrast, there was a significant difference in the mean maternal concern score in the test group before and after the intervention (P < 0.01). Conclusions: Given the effectiveness of Betty Neuman’s systems model, it can be used as a low-cost, effective care method to reduce maternal stress as the model was developed for understanding clients’ and caregivers’ needs and reducing their stress.