To examine the association between depressive symptoms and metabolic profile in women with prior gestational diabetes mellitus (GDM) and early postpartum prediabetes, and to explore whether a mobile-based lifestyle intervention affected mental health outcomes. Secondary, exploratory analysis of a multi-centric randomized controlled trial (MELINDA), evaluating a mobile-based lifestyle intervention versus standard follow-up (control group) in women with prediabetes after GDM. The analysis included 166 participants who completed the Center for Epidemiologic Studies-Depression (CES-D) questionnaire [score of ≥16 being suggestive for (sub)clinical depression] at baseline (6-16 weeks postpartum) and one year post-randomization. At one year, 26.5% of women (n = 44) reported depressive symptoms, with no significant difference between the intervention and control groups (30.5% vs. 22.6%, = 0.293). Women with depressive symptoms (symptomatic women) were younger (30.9 ± 4.9 vs. 32.5 ± 3.8 years, = 0.033) and were less often highly educated (61.4% vs. 80.3%, = 0.028). At baseline, symptomatic women had a higher rate of metabolic syndrome (38.6% vs. 21.9%, = 0.044), higher LDL-cholesterol [3.2 ± 0.8 vs. 2.8 ± 0.8 mmol/L, = 0.009], lower quality of life (lower SF-36 scores, < 0.050) and a higher level of anxiety based on the STAI-6 questionnaire (14.5 ± 3.6 vs. 11.2 ± 2.6, < 0.001). These differences persisted at one year postpartum with worse metabolic profile, more anxiety and lower quality of life in symptomatic women. Depressive symptoms are common in women with prediabetes in early postpartum after GDM and are associated with a persistent worse metabolic profile, increased anxiety and lower quality of life postpartum. The mobile-based lifestyle intervention did not improve mental health.