On March 12, 2019, Parker signed a new two-year contract with the Dolphins through the 2020 season. In Week 4 against the Los Angeles Chargers, Parker caught four passes for receiving yards 70 yards and one receiving touchdown in the 30–10 loss. In Week 11 against the Buffalo Bills, Parker caught seven passes for 135 yards in the 37–20 loss. In Week 13 against the Philadelphia Eagles, Parker caught seven passes for 159 yards and two touchdowns in the 37–31 win. On December 13, 2019, Parker signed a four-year, $40 million contract extension with the Dolphins. In Week 16 against the Cincinnati Bengals, Parker caught five passes for 111 yards and a touchdown during the 38–35 overtime win. In Week 17 against the New England Patriots, Parker caught eight passes for 137 yards during the 27–24 win. Overall in the 2019 season, Parker had his most productive season to date, catching 72 passes for 1,202 yards and nine touchdowns, which are all career-highs.