BackgroundThe incidence of application of medicinal herbs during pregnancy has increased significantly among women over the past years; however, the safety and efficacy of medicinal herbs during pregnancy are still unclear. The aim of the present study was to categorize the predictors of self-medication with herbal remedies during pregnancy based on the theory of planned behavior (TPB).MethodsThe present descriptive-analytical study was conducted on 300 pregnant women referred to Kashan health center to receive prenatal care services in 2020. The study participants were randomly selected using stratified random sampling with proportional allocation. The data collection tool was a two-part researcher made questionnaire. The first part of the questionnaire included demographic information, midwifery information, and questions related to women’s awareness about herbal medicine. The second part of the questionnaire was designed based on the theory of planned behavior including attitudes, perceived behavioral control, subjective norms, intention, and behavior performance. Data were analyzed using descriptive statistics, regression analysis, and SPSS version 18.0.ResultsThe mean age of participants was 28. 7±5.4 years (range, 15–45 years), the majority were housewives (88.3%) and had secondary education (39.3%). A total of 164 women (57. 1%) used medicinal herbs during pregnancy. The individual’s attitude towards herbal medicines consumption, subjective norm, and perceived behavioral control was correlated with behavioral intention (P < 0.05). Similarly, subjective norms were the most predictor of using herbal medicine among pregnant women (P < 0.05).ConclusionThe findings revealed that more than 50 % of pregnant women used medicinal herbs during pregnancy. The present study showed that the individual’s attitude towards herbal medicines consumption, subjective norm, and perceived behavioral control was correlated with intention of herbal medicine use among pregnant women. Likewise, subjective norms were the most predictor of herbal medicine use among pregnant women. The TPB should be addressed in planning health education programs and modifying health behaviors, including self-medication, especially during pregnancy.