2018 Davis Cup Americas Zone Group III

The Americas Zone was the unique zone within Group 3 of the regional Davis Cup competition in 2018. The zone's competition was held in round robin format in Escazú, Costa Rica, from 28 May to 2 June 2018. The two winning nations won promotion to Group II, Americas Zone, for 2019.

Participating nations
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Inactive nations
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• Eastern Caribbean

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Draw
Date: 28 May–2 June

Location: Costa Rica Country Club, Escazú, Costa Rica (hard)

Format: Round-robin basis. The winner of Pool A will play-off against the runner-up of Pool B and the winner of Pool B will play-off against the runner-up of Pool A to determine which two nations will advance to Americas Zone Group II in 2019.

Seeding

 * 1 Davis Cup Rankings as of 9 April 2018

Pool B
''Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-team ties, head-to-head records; 4. in three-team ties, (a) percentage of sets won (head-to-head records if two teams remain tied), then (b) percentage of games won (head-to-head records if two teams remain tied), then (c) Davis Cup rankings.''

Playoffs
' and ' were promoted to Group II in 2019.