The objective of this study is to determine the healthy behaviors of mothers with gestational diabetes mellitus (GDM) in Ardabil in 2020. An analytic cross-sectional study was conducted on 360 mothers with GDM in Ardabil in 2020. Self-reported data was collected using a sociodemographic and a lifestyle questionnaire (LSQ) with assistance from health staff. Univariate and multivariate linear regression tests were used to assess risk variables associated with health behaviors and GDM. The total score of the LSQ was 123.6 ± 9.9, which was considered fair or average. The participants’ age had a significant relationship with physical health (beta = −.093, P = .004), weight control and nutrition (beta = .094, P = .010), and psychological health (beta = .081, P = .005). Higher educational level was associated with accident prevention (beta = .453, P = .001). Participants’ occupation had a significant positive relationship with the prevention of diseases (beta = .925, P = .003). A gravida of the participants was associated with weight control and nutrition (beta = −.497, P = .016). Body mass index was associated with physical health (beta = −.179, P = .001), exercise and fitness (beta = −.149, P = .016), psychological health (beta = −.158, P = .001), accident prevention (beta = .098, P = .023), and total score of LSQ (beta = −.559, P = .006). The findings of this study showed that mothers with GDM had LSQ subscales scores considered fair or average, except for the prevention of diseases and avoidance of drugs, alcohol, and opiates subscales, which were considered good.