The prevalence of excess body weight (overweight plus obesity) in children has risen during the last decades in many countries, but it is unclear whether it has reached a plateau in Spanish children. We performed an updated systematic review and meta-analysis for the prevalence of excess body weight in children from Spain, comparing the trends between 1999 and 2010 and 2011 and 2021. Data were reported in a prior meta-analysis, plus an updated search using the Web of Science, MEDLINE (via PubMed) and EMBASE databases for data from January 2018 until December 2021. Thirteen representative studies were identified (34,813 children aged 2 to 13 years), with sample sizes averaging 2678 (range: 396–16,665). The prevalence of excess body weight in Spanish children aged 2 to 6 years increased from 23.3% (95% CI, 18.5% to 25.5%) during the period 1999–2020 to 39.9% (95% CI, 35.4% to 44.7%) during 2011–2021. In children aged 7 to 13 years, the prevalence of excess body weight increased from 32.3% (95% CI, 29.1–35.6%) during the period 1999–2020 to 35.3% (95% CI, 32.9–37.7%) during 2011–2021. The prevalence of childhood overweight and obesity in Spain has substantially increased in the last decade. New food policies to address the childhood obesity epidemic are urgently required to reverse current trends.