Vic Tafur of The Athletic first reported the meeting.
The 31-year-old University of Minnesota product is coming off a mundane season with the Titans. He tallied 54 catches for 563 yards and one touchdown. Pro Football Focus graded him as the league's No. 60 wideout, right on the fringe of starter-level performance.
He missed all but three games with the New York Jets in 2016 because of a shoulder injury, but before that he was one of the league's most reliable targets.
Decker recorded at least 80 receptions for 1,000 yards and 11 scores in three of four seasons from 2012 through 2015 with the Jets and Denver Broncos, who selected him in the third round of the 2010 draft.
Oakland, which has already added 32-year-old wide receiver Jordy Nelson and 29-year-old running back Doug Martin, would be seeking late-career resurgences from that triumvirate to help recharge the offense if they sign Decker after a disappointing 2017 campaign.
He'd likely operate out of the slot with Nelson and Amari Cooper on the outside for quarterback Derek Carr as part of an offense that also features veteran rusher Marshawn Lynch.