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.
Date: 28 May–2 June Location: Costa Rica Country Club, Escazú, Costa Rica (hard) Format: Round-robin basis.
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.
Bahamas and Honduras were promoted to Group II in 2019.