Background: Both insufficient and excessive iodine intake can lead to a broad range of disorders. A cross-sectional survey was conducted to assess iodine status in schoolchildren from Croatia. Design: 957 healthy 6 to 12-year-olds were enrolled (381 from northwestern region, 190 from eastern region, 215 from north Adriatic, and 171 from central Dalmatia region). Urinary iodine concentration (UIC) was measured in spot urine samples. Thyroid volume (Tvol) was recorded by ultrasound device. Standard anthropometric measures were taken, and body surface area (BSA) was determined. Tvol medians were calculated as a function of age, sex and BSA and compared with reference values. Results: Total sample size included 490 boys and 467 girls. Overall median UIC was 250.68 µg/L, with statistically significant variance in geographical regions (median UIC was 244.71 µg/L in northwestern, 208.02 µg/L in eastern, 216.07 µg/L in north Adriatic and 366.43 µg/L in central Dalmatia region). There were 10.08% of samples with UIC < 100 mcg/L while 38.24% of samples had UIC > 300 mcg/L. Age-matched Tvol medians in schoolchildren from all regions of Croatia were at the upper limits of reference values, but in north Adriatic and central Dalmatia exceeded the 97th percentile. BSA-matched Tvol was within the reference range in all regions. Conclusions: Our results demonstrate sufficient (more than adequate) iodine intake in schoolchildren of Croatia, and excessive iodine intake in central Dalmatia region. Total thyroid volumes in schoolchildren of Croatia were within the normal range, however borderline enlarged age-matched thyroid glands were observed in coastal areas.