Introduction Our aim was to evaluate the effect of dietary and lifestyle advice given to women who were overweight or obese during pregnancy on maternal quality of life, anxiety and risk of depression, and satisfaction with care. Material and methods We conducted a randomized trial, involving pregnant women with body mass index ≥25 kg/m2, recruited from maternity units in South Australia. Women were randomized to Lifestyle Advice or Standard Care, and completed questionnaires assessing risk of depression (Edinburgh Postnatal Depression Scale), anxiety (Spielberger State-Trait Anxiety Inventory), and quality of life (SF-36) at trial entry, 28 and 36 weeks' gestation, and 4 months postpartum. Secondary trial outcomes assessed for this analysis were risk of depression, anxiety, maternal quality of life, and satisfaction with care. Results One or more questionnaires were completed by 976 of 1108 (90.8%) women receiving Lifestyle Advice and 957 of 1104 (89.7%) women receiving Standard Care. The risk of depression [adjusted risk ratio 1.01; 95% confidence interval (CI) 0.82-1.24; p = 0.95], anxiety (adjusted risk ratio 1.09; 95% CI 0.93-1.27; p = 0.31), and health-related quality of life were similar between the two groups. Women receiving Lifestyle Advice reported improved healthy food choice [Lifestyle Advice 404 (68.9%) vs. Standard Care 323 (51.8%); p < 0.0001], and exercise knowledge [Lifestyle Advice 444 (75.8%) vs. Standard Care 367 (58.8%); p < 0.0001], and reassurance about their health [Lifestyle Advice 499 (85.3%) vs. Standard Care 485 (77.9%); p = 0.0112], and health of their baby [Lifestyle Advice 527 (90.2%) vs. Standard Care 545 (87.6%); p = 0.0143]. Conclusion Lifestyle advice in pregnancy improved knowledge and provided reassurance without negatively impacting well-being.