The study aimed to determine the effects of high-risk pregnancy on prenatal stress levels. The study was conducted with a case-control design in Turkey in September-December 2019. The sample included pregnant women diagnosed with high-risk pregnancy and were at their 36th or later gestational weeks as the case group (n = 121) and healthy pregnant women as the control group (n = 245). The Antenatal Perceived Stress Inventory (APSI) and the Revised Prenatal Distress Questionnaire (NUPDQ-17 Item Version) were used to assess the stress levels of the participants in the study. It was determined that high-risk pregnancy was associated with higher rates of prenatal stress (APSI: p < 0.001, effect size = 0.388; NUPDQ: p = 0.002, effect size = 0.272) compared to the control group. The results of the linear regression analysis showed that high-risk pregnancy affected APSI (R2 = 0.043, p < 0.001) and NUPDQ (R2 = 0.033, p = 0.009) scores, but education levels, number of pregnancies, and number of abortions did not affect APSI and NUPDQ scores. According to the results of this study, high-risk pregnant women are in a risk group for stress. It is of great importance for the course of a pregnancy that healthcare professionals assess the stress levels of pregnant women in the high-risk pregnancy category and provide psychological support to pregnant women who have high stress levels or are hospitalized.