Background: Disadvantaged communities provide adverse psychosocial exposures that have been linked to high levels of stress, and this may provide one explanatory pathway linking socioeconomic disadvantage to obesity. The analysis of cortisol concentrations in hair represents a valuable biomarker for retrospective measurement of chronic stress, however it has not been used to examine associations between stress and obesity among disadvantaged individuals. This study used hair cortisol analysis to quantify associations between stress and body mass index (BMI), and between objective and perceived stress levels, in women and children living in socioeconomically disadvantaged neighbourhoods. Methods: Participants were a volunteer sample of disadvantaged women and children from the Resilience for Eating and Activity Despite Inequality (READI) study. Data from 70 women, including 30 maternal-child pairs, were analysed. Women self-reported body weight, height and perceived stress scale (PSS) scores. Children’s body weight and height were measured. Women reported sociodemographic variables and provided hair samples for themselves and their child. Hair cortisol levels were measured using enzyme-linked immunosorbent assay. Multiple linear regression assessed associations between stress and BMI, and between objective and perceived stress levels in women and children. Results: Women's hair cortisol levels were not associated with their BMI or PSS scores. Women’s PSS scores were associated with their BMI (p=0.015). Within maternal-child pairs, mothers and children’s hair cortisol levels were strongly associated (p=0.006). Maternal hair cortisol levels and PSS scores were unrelated to their child's zBMI. Children's hair cortisol levels were not associated with their zBMI or with their mother's PSS score. Conclusions: Objective and subjective measures of stress may be distinct. Subjective measures may be more important predictors of weight-related risk. These findings provide a platform for future, larger studies that can elucidate the pathways implicated in these results.