He played college football for the Alabama Crimson Tide, and was selected by the Miami Dolphins in the first round of the 2018 NFL draft before being traded to the Steelers during the 2019 season.

In the 2016 SEC Championship Game against Florida, Fitzpatrick broke the Alabama all-time record for career interceptions returned for a touchdown (4).

[28] Head coach Adam Gase named Fitzpatrick the primary backup safety to begin the regular season, behind starters McDonald and Reshad Jones.

On September 9, 2018, Fitzpatrick made his professional regular season debut in the Miami Dolphins' home-opener against the Tennessee Titans in Week 1 and recorded six combined tackles (three solo) as well as breaking up a pass, in their 27–20 victory.

[29] In Week 3, he earned his first career start after Reshad Jones was declared inactive due to a shoulder injury and finished the Dolphins' 28–20 victory over the Oakland Raiders with ten combined tackles (two solo).

[30] On September 30, 2018, he collected ten combined tackles (four solo), two pass deflections, and made his first career interception off a throw by quarterback Tom Brady intended for wide receiver Phillip Dorsett during a 38–7 loss at the New England Patriots.

[35] On December 31, 2018, the Miami Dolphins fired head coach Adam Gase after they finished the 2018 NFL season with a 7–9 record and missed the playoffs.

[37][38] On September 8, 2019, he started in the Miami Dolphins' home-opener at nickelback and recorded six combined tackles (four solo) in a 59–10 loss to the Baltimore Ravens.

The following week, Fitzpatrick made four combined tackles (three solo), two pass deflections, one interception, and scored a touchdown after he had a 43-yard return after he recovered a fumble teammate Javon Hargrave caused while sacking Jared Goff during a 17–12 victory against the Los Angeles Rams.

His interception happened during a pass attempt by Jared Goff with less than a minute left in the fourth quarter, sealing the Steelers' victory.

[57] On April 27, 2021, the Pittsburgh Steelers chose to exercise the fifth-year option on Fitzpatrick's rookie contract, worth a guaranteed $10.61 million for the 2022 season.

[58][59] Head coach Mike Tomlin chose to remain with Fitzpatrick and Terrell Edmunds as the starting safety tandem to kickoff the regular season.

On December 5, 2021, he made nine combined tackles (seven solo), a pass deflection, and had an interception on a throw by Lamar Jackson to tight end Mark Andrews during a 19–20 win against the Baltimore Ravens,.

He ended the 2021 NFL season with a total of 124 combined tackles (84 solo), two interceptions, seven passes defended, and one forced fumble in 16 games and 16 starts.

[27] With an annual salary of $18.4 million, he became the highest paid safety in the NFL at the time, later being surpassed by Derwin James of the Los Angeles Chargers.

On January 1, 2023, Fitzpatrick made nine combined tackles (four solo), had a pass deflection, and had an interception on a throw by Lamar Jackson during a 16–13 victory at the Baltimore Ravens.

[72] Head coach Mike Tomlin named Fitzpatrick and Keanu Neal the starting safeties to begin the regular season.

[74] On December 16, 2023, Fitzpatrick injured his left knee in the second quarter of a 13–30 loss to the Indianapolis Colts and was inactive for the last three games of the season (Weeks 16–18).

In Week 5, he collected a season-high ten combined tackles (eight solo) and had one pass deflection as the Steelers lost 17–20 to the Dallas Cowboys.

[78] He finished the 2024 NFL season with a total of 96 combined tackles (64 solo), four pass deflections, one interception, and a forced fumble while starting all 17 games.