IntroductionHeight, body mass index (BMI), and weight gain are associated with breast cancer risk in the general population. It is unclear whether these associations also exist for carriers of pathogenic variants in theBRCA1orBRCA2genes.Patients and methodsAn international pooled cohort of 8091BRCA1/2variant carriers was used for retrospective and prospective analyses separately for premenopausal and postmenopausal women. Cox regression was used to estimate breast cancer risk associations with height, BMI, and weight change.ResultsIn the retrospective analysis, taller height was associated with risk of premenopausal breast cancer forBRCA2variant carriers (HR 1.20 per 10 cm increase, 95% CI 1.04–1.38). Higher young-adult BMI was associated with lower premenopausal breast cancer risk for bothBRCA1(HR 0.75 per 5 kg/m2, 95% CI 0.66–0.84) andBRCA2(HR 0.76, 95% CI 0.65–0.89) variant carriers in the retrospective analysis, with consistent, though not statistically significant, findings from the prospective analysis. In the prospective analysis, higher BMI and adult weight gain were associated with higher postmenopausal breast cancer risk forBRCA1carriers (HR 1.20 per 5 kg/m2, 95% CI 1.02–1.42; and HR 1.10 per 5 kg weight gain, 95% CI 1.01–1.19, respectively).ConclusionAnthropometric measures are associated with breast cancer risk forBRCA1andBRCA2variant carriers, with relative risk estimates that are generally consistent with those for women from the general population.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13058-023-01673-w.