Lewis will earn a guaranteed $8 million.
In 15 games last year, the 25-year-old posted 59 combined tackles, 2.0 sacks, one fumble recovery and two pass deflections.
The free-agent cornerback market began moving quickly with William Jackson signing for three years, $40.5 million in Washington, Shaq Griffin taking three years, $40 million from the Jacksonville Jaguars and Ronald Darby getting three years, $30 million from the Denver Broncos.
Most importantly for Dallas, though, Chidobe Awuzie accepted a three-year, $21.8 million deal from the Cincinnati Bengals, ending a four-year tenure with the Cowboys.
Retaining Lewis became an immediate need once Awuzie departed. Now the third-round pick out of Michigan in 2017 is set to return to Dallas as one of the team's top players in the secondary alongside Maurice Canady and Trevon Diggs.
According to Spotrac, the Cowboys have $6.7 million remaining in available cap space.
Bringing Lewis back on a three-year deal doesn't preclude any additional signings for Dallas, but the team will need to be rather strategic about how it uses its cap space moving forward. That alone should make clear how important the front office felt Lewis is to the club's long-term success.