Haynos worked out for the Cowboys last week on their Dallas Day tryouts for local draftable prospects.
Haynos, 6-8, 270 pounds, did not play last year after he was released in training camp by Jacksonville. He entered the league with Green Bay in 2008 and spent parts of the next three seasons with Miami, catching 21 passes for 184 yards and three touchdowns.
The Cowboys have only two tight ends on the roster in Jason Witten and John Phillips. With coach Jason Garrett liking to use multiple tight end sets, the Cowboys have kept up to four tight ends on the 53-man roster in recent years.
The Cowboys signed Witten to an extension last season through 2017 and Phillips is signed through this season. The Cowboys have not drafted a tight end since taking Phillips in the sixth round in 2009.