Smiley, a six-year veteran, agreed to restructure the five-year, $25 million deal he signed with Miami in 2008. The Jaguars gave up a conditional seventh-round pick in hopes that Smiley will be able to upgrade the team's interior line.
Smiley passed a physical Tuesday, making the trade official.
To make room for Smiley on the roster, the Jaguars waived first-year running back Allen Patrick.
Smiley started 12 games for the Dolphins each of the past two seasons, but they put him on the trading block because of durability concerns.
Jacksonville struggled to run up the middle last season and protect quarterback David Garrard.