The Cowboys have been burned in the downfield passing game in recent years due to strong safety Roy Williams playing too close to the line of scrimmage, not to mention poor coverage from the free safety position in general.
Dallas drafted Florida State's Patrick Watkins as a free safety in the fifth round of last year's draft, but Watkins was largely inconsistent and may be best suited for a reserve role. In addition, one time starter Keith Davis is more in the mold of Williams as opposed to a free safety with strong coverage skills.
The Cowboys had been considering moving Anthony Henry from cornerback to free safety if no help was added either in the draft or free agency.
Hamlin was originally Seattle's second-round pick in 2003 and he has since started 52 of 54 regular-season games he played in.
Last season Hamlin recorded three sacks and two interceptions in 16 games, just a year after suffering life-threatening head injuries from a street fight in 2005.
For his career he has eight interceptions in four seasons.
Hamlin visited with Dallas Wednesday after visiting with the New Orleans Saints.
The Cowboys have also signed two other sought after free agents this offseason, including tackle Leonard Davis and quarterback Brad Johnson.
Davis is expected to start on the offensive line, either at right guard or right tackle and Johnson will serve as Tony Romo's backup.