The 2010 IIHF World U18 Championship Division I was an international under-18 ice hockey competition organised by the International Ice Hockey Federation. Both Division I tournaments made up the second level of the 2010 IIHF World U18 Championships. The Group A tournament was played in Herning, Denmark, and the Group B tournament was played in Krynica-Zdrój, Poland. Norway and Germany won the Group A and B tournaments respectively and gained promotion to the Top Division of the 2011 IIHF World U18 Championships.
The Group A tournament was played in Herning, Denmark, from 12 to 18 April 2010.
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<small>All times are local (UTC+2).</small>
The Group B tournament was played in Krynica-Zdrój, Poland, from 11 to 17 April 2010.
<section begin=Division I B/><section end=Division I B/>
<small>All times are local (UTC+2).</small>