BACKGROUND Pregnancy is associated with substantial stressful experiences. There are controversies concerning the positive and negative roles of social support during pregnancy. This research aimed to study the association of social support with the pregnancy-related stress. METHODS In the current cross-sectional research, 200 pregnant women were recruited through convenience sampling from two teaching hospitals affiliated with Babol University of Medical Sciences and a private obstetric clinic. The women completed two self-reported questionnaires during prenatal care appointments. The questionnaires included the Revised Prenatal Distress Questionnaire (NuPDQ) and Social Support Questionnaire (SSQ). RESULTS A significantly positive association was observed between the social support of neighbors and the total score of pregnancy stress (P<0.001), as well as the scores of its four subscales, namely medical problems (P<0.001), parenting (P=0.25), infant health stress (P=0.006), and pregnancy symptoms (P=0.001). Based on the linear regression models, the social support of neighbors was significantly related to the medical problem-associated stress in pregnant women (β = 0.147, 95% CI: 0.14 to 0.62, p = 0.047), pregnancy symptom (β = 0.203, 95% CI: -0.01 to 0.327, p = 0.017), and fear of childbirth (β = 0.164, 95% CI: 0.05 to 0.38, p = 0.046). Furthermore, the neighbors' social support (β = 0.172, 95% CI: 0.02 to 0.32, p = 0.04) and the total score of social support (β = 0.155, 95% CI: 0.01 to 0.304, p = 0.046) were significantly associated with the total score of pregnancy stress. CONCLUSIONS Neighbors' support, as a component of social support, was found to be significantly related to pregnancy stress. This study recommends that healthcare providers consider the positive and negative impacts of social support during the pregnancy period.