Maternal anxiety and depression during pregnancy and early childhood have been associated with child anxiety and attention-deficit/hyperactivity disorder (ADHD). However, previous studies are limited by their short follow-up, few assessments of maternal symptoms, and by not including maternal and child ADHD. The present study aimed to fill these gaps by investigating whether maternal anxiety and depressive symptoms from pregnancy to child age 5 years increase the risk of child anxiety disorders at age 8 years. This study is part of the population-based Norwegian Mother, Father, and Child Cohort Study. Maternal anxiety and depressive symptoms were assessed by the Hopkins Symptom Checklist (SCL) six times from pregnancy through early childhood, and ADHD symptoms by the Adult Self-Report Scale (ASRS). At age 8 years (n = 781), symptoms of anxiety disorders and ADHD were assessed, and disorders classified by the Child Symptom Inventory-4. Logistic regression models estimated the risk of child anxiety depending on maternal symptoms. The mothers of children classified with an anxiety disorder (n = 91) scored significantly higher on the SCL (at all time points) and ASRS compared with the other mothers. In univariable analyses, maternal anxiety and/or depression and ADHD were associated with increased risk of child anxiety (odds ratios = 2.99 and 3.64, respectively), remaining significant in the multivariable analysis adjusted for covariates. Our findings link maternal anxiety, depression, and ADHD during pregnancy and early childhood to child anxiety at age 8 years.