McKivitz redshirted his true freshman season.[7] He became the Mountaineers' starting left tackle four games into his redshirt freshman season after starter Yodny Cajustetore his ACL and McKivitz started the final ten games of the season.[8] As a redshirt sophomore, he moved to right tackle, starting all 13 games and earning honorable mention All-Big 12 Conference honors. McKivitz started all 12 of the Mountaineers, games as a redshirt junior.[9] He moved back to left tackle going into his redshirt senior season and was named first-team All-Big 12, the Big 12 co-Offensive Lineman of the Year and a second-team All-American by Walter Camp and the Associated Press's third-team.[10][11][12]
McKivitz was selected in the fifth round of the 2020 NFL draft with the 153rd pick by the San Francisco 49ers.[15] The 49ers previously acquired the selection from the Miami Dolphins by trading Matt Breida to Miami. He made his NFL debut in Week 2 against the New York Jets, playing eight snaps on offense and five snaps on special teams.[16] McKivitz made his first career start on November 29, 2020, lining up at right guard and playing all 72 of the 49ers offensive snaps in a 23–20 win over the Los Angeles Rams.[17] He was placed on the reserve/COVID-19 list by the team on December 16, 2020,[18] and activated on December 25.[19]
On August 31, 2021, McKivitz was waived by the 49ers and re-signed to the practice squad the next day.[20][21] He was promoted to the active roster on November 10, 2021.[22]
On March 10, 2022, McKivitz re-signed with the 49ers.[23] McKivitz suffered a high ankle sprain in Week 4 and was placed on injured reserve on October 8, 2022.[24] He was activated on November 12.[25]
On March 9, 2023, McKivitz signed a two-year contract extension with the 49ers.[26] McKivitz replaced Mike McGlinchey as starter after McGlinchey departed in Free Agency for this Denver Broncos that summer. During the 2023 season McKivitz started all 17 games and was a starter in Super Bowl LVIII. The 49ers lost to the Chiefs 25–22 in overtime.[27]
On March 13, 2024, McKivitz signed a one-year, $7 million contract extension with the 49ers through the 2025 season.[28] On September 8, 2025, McKivitz signed a three-year, $45 million contract extension with the 49ers that runs through the 2028 season.[29]