When Jacksonville selected Jalen Ramsey fifth overall out of Florida State in the 2016 NFL Draft, they were bringing in a consensus national champion and two-time All-American expected to instantly redefine their secondary. Ramsey met those towering expectations immediately, stepping onto the field with supreme swagger, elite physical coverage skills, and a willingness to tackle in space that earned him PFWA All-Rookie Team honors right out of the gate.

Ramsey quickly became the premier, vocal cornerstone of Jacksonville's formidable "Sacksonville" defense. His peak performance came during the historic 2017 campaign, when he erased opposing top receivers week after week, racking up 17 pass deflections and four interceptions—including a game-sealing interception late in the fourth quarter of the wild-card victory over Buffalo. That season earned him his first Pro Bowl selection and First-Team AP All-Pro honors while driving the Jaguars to the AFC Championship Game. He followed up with another Pro Bowl nod in 2018, routinely taking away half the field and asserting himself as arguably the best shutdown cornerback in professional football. However, his explosive tenure in North Florida collapsed early in the 2019 season following a heated sideline altercation with head coach Doug Marrone and a subsequent trade request. In October 2019, Jacksonville traded Ramsey to the Los Angeles Rams for a massive haul that included two first-round picks, and he later won Super Bowl LVI.

In Jacksonville, Ramsey had nine picks with 242 combined tackles.