<p>Understanding the social and structural determinants that affect children’s access to SARS-CoV-2 testing and their infection risk informs policies to reduce health inequalities. However, evidence on testing and test positivity among immigrant young children in Europe is limited. We linked national laboratory surveillance data, primary health care records, and cohort baseline data for children born in 2018 and 2020 living in four municipalities in the Lisbon Metropolitan Area to analyse determinants of SARS-CoV-2 testing and positivity rates. Our analysis focused on migratory status and considered perinatal characteristics, socioeconomic conditions, and whether the child had an assigned family doctor. A lower prevalence of being tested at least once was observed among immigrant children compared with non-immigrant children. Among those tested, immigrants showed a lower prevalence of at least one positive test. In adjusted models, being tested at least once was associated with migratory status, daytime location (preschool or home), and having a family doctor (yes/no), whereas test positivity was only associated with migratory status. In this setting, testing appears to be driven by symptoms or contact suspicion, suggesting informational, social, and structural barriers that limit equitable access to testing and primary health care for immigrant children.</p>