The 2018 World Junior Ice Hockey Championship Division I consisted of two tiered groups of six teams each: the second-tier Division I A and the third-tier Division I B. For each tier's tournament, the team which placed first was promoted to the next highest division, while the team which placed last was relegated to a lower division. The tournaments were a round-robin tournament format, with two points allotted for a win, one additional point for a regulation win, and one point for an overtime or game winning shots loss.