The deal assures Cason will be in camp when the team holds its first full-squad practice on Friday.
"It's a big relief," Cason said. "Of course I was concerned but I had faith that it would get done. All I could do was work out and control the things I was able to control and that was that. I didn't worry about it too much because I knew it would get done, so I did the things I could control."
Cason was the team's last draft pick to sign. He missed three days of rookie camp.
The 27th overall pick finished his college career at Arizona with 15 interceptions.
Information from the Associated Press was included in this report