Early interventions may promote reductions in mothers' anxiety-depression (AD) symptoms and improvements in their offspring. This longitudinal randomized research was conducted to assess the effects of interdisciplinary online therapeutic groups (GIO) in at-risk mothers and babies during the COVID-19 pandemic in a disadvantaged neighborhood in Barcelona (Spain). A total of 135 babies were born from March 2020 to June 2021 in a primary healthcare center of Barcelona (Spain). Pregnant woman and new mothers were screened for AD symptomatology through EPDS and STAI questionnaires. Seventy-two of them met high-risk criteria for AD and were included in the study. They were randomly assigned into the two groups of the study: 40 participants were assigned to GIO, the therapeutic group (TG), while 32 of them were assigned to the control group (CG) and received treatment as usual. The course of the mothers' symptomatology was assessed, as well as the baby's development at 6 months old in a blind pediatric follow-up. No differences were found in AD between both groups before the intervention. However, we obtained a significant decrease in AD symptomatology (EPDS p < .001; STAI state p = .015 and STAI trait p < .001at 6 months of life) after the intervention in the TG compared to the CG. Pediatric follow-up at 6 months demonstrated significant differences between groups in babies' development assessment (manipulation p = .003; language p < .001; sociability p < .001). The GIO helped to ensure healthy development of the baby and reduction of the mothers' depressive-anxiety symptomatology.