Maternal stress has been associated with pregnancy complications and negative perinatal outcomes. The effectiveness of a stress management program (including diaphragmatic breathing, progressive muscle relaxation, and guided imagery) was tested in a 2-arm, parallel-group, quasi-experimental randomized controlled trial of an 8-week intervention group comprising pregnant women in the second trimester (N=40), compared with a usual care wait-list control group. Self-report measures were used to evaluate perceived stress levels (Perceived Stress Scale), health locus of control (Health Locus of Control Scale), and depressive symptoms (Edinburgh Postnatal Depression Scale). Data analysis showed that stress management techniques significantly lowered perceived stress levels and depressive symptoms (p < .05) and increased the internal locus of control (p < .05). Stress management using recorded relaxation instructions and handouts is a cost-effective intervention that can improve pregnant women's mental well-being. © 2018 American Psychological Association.