In Week 14, McKinney earned his first career start, recording four combined tackles (one solo) during a 7–26 loss to the Arizona Cardinals.

On January 3, 2021, McKinney recorded a season-high eight combined tackles (four solo) and made his first career interception off a pass by quarterback Andy Dalton that was intended for tight end Dalton Schultz in the end zone with 1:24 remaining in the fourth quarter, clinching a 23–19 victory against the Dallas Cowboys.

McKinney entered training camp as a backup safety as Logan Ryan and Jabrill Peppers were entrenched as the starters.

[30] On October 17, 2021, McKinney made three solo tackles, a season-high two pass deflections, and tied his career-high with two interceptions thrown by Matthew Stafford and John Wolford as the Giants were defeated by the Los Angeles Rams 38-11.

[32] On November 7, 2021, McKinney recorded seven combined tackles (four solo), two pass deflections, two interceptions, and a touchdown in a 23–16 victory at the Las Vegas Raiders.

During the third quarter, Derek Carr attempted a pass to wide receiver Hunter Renfrow, but it was picked off by McKinney and returned 41+yards to score the first touchdown of his career.

[35] He finished the 2021 NFL season with a total of 93 combined tackles (59 solo), ten pass deflections, five interceptions, and a touchdown while appearing in all 17 games and starting 16.

[36] On January 11, 2022, the New York Giants announced their decision to fire head coach Joe Judge after they finished the 2021 NFL season with a 4-13 record.

[37] He entered training camp projected to be a starter after Logan Ryan and Jabril Peppers both departed during free agency.

[42] In Week 11, McKinney collected a season-high 13 combined tackles (eight solo) and two pass deflections during a 31–19 victory at the Washington Commanders.

[47][48] On September 6, 2024, McKinney made his debut with the Green Bay Packers and recorded four combined tackles (three solo), a pass deflection, and had his first interception with the Packers on a pass thrown by Jalen Hurts to wide receiver DeVonta Smith in the first quarter of a 34–29 loss to the Philadelphia Eagles.

In Week 3, he continued his interception streak with a third pick off Will Levis, while also amassing five combined tackles (four solo) and a pass deflection during a 30–14 win at the Tennessee Titans.

He started all 17 games in 2024 and amassed a total of 88 combined tackles (60 solo), 11 pass deflections, a career-high eight interceptions, and a fumble recovery.