Background: Social well‐being, including prosocial and peer relationship skills, independence and co‐operation, is a particularly important developmental outcome in intellectual disability (ID). The present study investigated pathways to social well‐being through the early years' family environment, particularly the role of parental investments in mediating the path from family poverty to child social well‐being. Methods: In line with the Family Investment Model (FIM), we tested whether parental investments between 3 and 5 years of age mediate the impact of family poverty at 9 months of age on children's social well‐being at 7 years. Structural equation models were fitted to data from 555 children with ID identified from a UK population‐based cohort. Results: Findings indicated that home learning investments and the structural home environment (though not play) significantly mediated the effect of family poverty on children's social skills, albeit in different directions. While all parental investments reduced in the presence of poverty, the home learning environment appeared to promote social well‐being, whereas the structural home environment did not. Sensitivity analyses controlling for co‐occurring autism confirmed the pattern of findings. Child gender, ethnicity and parental educational qualifications did not moderate the mediational relationships, suggesting that FIM pathways to social well‐being were relevant to all families. Conclusions: The FIM provides a helpful framework to map developmental pathways for children with an ID. Parental investments related to home learning, the structural home environment and play are reduced in the presence of poverty although their impact on child social well‐being appears to differ.