Background and Aim: The present study was conducted to determine the effectiveness of cognitive behavioral therapy (CBT) on anxiety sensitivity, pregnancy stress, and mindfulness in primiparous women. Method: This quasi-experimental study used a pretest–posttest design with a control group. The population consisted of primiparous women attending health centers in Babolsar during 2024–2025 A sample of 30 women (15 in the experimental group and 15 in the control group) was selected through convenience sampling and randomly assigned to the groups. The instruments included the Anxiety Sensitivity Index (ASI), Pregnancy Distress Questionnaire (PDQ), and Kentucky Inventory of Mindfulness Skills (KIMS). The intervention consisted of 8 weekly group sessions of cognitive behavioral therapy based on the protocol of Antony et al. (2007), adapted for pregnancy. Data were analyzed using multivariate analysis of covariance (MANCOVA) and analysis of covariance (ANCOVA). Results: Significant differences were found in favor of the experimental group on all variables and subscales (p < 0.001), with large effect sizes (η² = 0.424–0.894). Conclusion: Short-term cognitive behavioral therapy is an effective, safe, and feasible approach that can be implemented in health centers to reduce psychological problems in primiparous women.