| District | Vacated by | Reason for change | Successor | Date of successor'sformal installation |
| Kansas 4 | Mike Pompeo(R) | Resigned January 23, 2017, to become Director of the Central Intelligence Agency.A special election was held April 11, 2017. | Ron Estes(R) | April 25, 2017 |
| California 34 | Xavier Becerra(D) | Resigned January 24, 2017, to become Attorney General of California.A special election was held June 6, 2017. | Jimmy Gomez(D) | July 11, 2017 |
| Georgia 6 | Tom Price(R) | Resigned February 10, 2017, to become U.S. Secretary of Health and Human Services.A special election was held June 20, 2017. | Karen Handel(R) | June 26, 2017 |
| South Carolina 5 | Mick Mulvaney(R) | Resigned February 16, 2017, to become Director of the Office of Management and Budget.A special election was held June 20, 2017. | Ralph Norman(R) | June 26, 2017 |
| Montana at-large | Ryan Zinke(R) | Resigned March 1, 2017, to become U.S. Secretary of the Interior.A special election was held May 25, 2017. | Greg Gianforte(R) | June 21, 2017 |
| Utah 3 | Jason Chaffetz(R) | Resigned June 30, 2017, for personal reasons.A special election was held November 7, 2017. | John Curtis(R) | November 13, 2017 |
| Pennsylvania 18 | Tim Murphy(R) | Resigned October 21, 2017.A special election was held March 13, 2018. | Conor Lamb(D) | April 12, 2018 |
| Michigan 13 | John Conyers(D) | Resigned December 5, 2017. A special election was held November 6, 2018. | Brenda Jones(D) | November 29, 2018 |
| Arizona 8 | Trent Franks(R) | Resigned December 8, 2017. A special election was held April 24, 2018. | Debbie Lesko(R) | May 7, 2018 |
| Ohio 12 | Pat Tiberi(R) | Resigned January 15, 2018, to lead the Ohio Business Roundtable.A special election was held August 7, 2018 | Troy Balderson (R) | September 5, 2018 |
| New York 25 | Louise Slaughter(D) | Died March 16, 2018. A special election was held November 6, 2018. | Joseph Morelle(D) | November 13, 2018 |
| Texas 27 | Blake Farenthold(R) | Resigned April 6, 2018.A special election was held June 30, 2018. | Michael Cloud(R) | July 10, 2018 |
| Oklahoma 1 | Jim Bridenstine(R) | Resigned April 23, 2018, to become the Administrator of National Aeronautics and Space Administration.Successor was elected to the next term and, by Oklahoma law, was considered thereby "appointed" November 6, 2018, to finish the current term.[citation needed] There is debate about the legality of such an appointment, however.[citation needed] | Kevin Hern(R) | November 13, 2018 |
| Pennsylvania 7 | Pat Meehan(R) | Resigned April 27, 2018.A special election was held November 6, 2018. | Mary Gay Scanlon(D) | November 13, 2018 |
| Pennsylvania 15 | Charlie Dent(R) | Resigned May 12, 2018.A special election was held November 6, 2018. | Susan Wild(D) | November 27, 2018 |
| Florida 6 | Ron DeSantis(R) | Resigned September 10, 2018, to focus on his gubernatorial campaign.Seat remained vacant until determined by general election. | Vacant until the next Congress |
| West Virginia 3 | Evan Jenkins(R) | Resigned September 30, 2018, to become justice of the Supreme Court of Appeals of West Virginia.Seat remained vacant until determined by general election. |
| New Mexico 1 | Michelle Lujan Grisham(D) | Resigned December 31, 2018, to become Governor of New Mexico. |
