See main article: 2018 Fed Cup Americas Zone. The play-offs of the 2018 Fed Cup Americas Zone Group I were the final stages of the Group I Zonal Competition involving teams from the Americas. Using the positions determined in their pools, the seven teams faced off to determine their placing in the 2018 Fed Cup Americas Zone Group I. The winner of the promotion play-off advanced to World Group II play-offs, and the losers of the relegation play-off were relegated down to the Americas Zone Group II.
| Placing | Pool A | Pool B |
|---|---|---|
| 1 | ||
| 2 | ||
| 3 | ||
| 4 | ||
The first placed teams of the two pools were drawn in head-to-head rounds. The winner advanced to the World Group II play-offs.
The runner-up teams of the two pools were drawn in head-to-head to determine the third and fourth placings.
The bottom team of Pool A and the third placed team of Pool B were drawn in head-to-head. The loser was relegated down to Americas Zone Group II in 2019. The last placed team of Pool B (Guatemala) was automatically relegated.
| Placing | Teams | ||
| Promoted/First | |||
| Second | |||
| Third | |||
| Fourth | |||
| Fifth | |||
| Relegated/Sixth | |||