McClain was cut last week by the Ravens, saving the team $3.2 million against the salary cap.
McClain has three other NFL teams interested in him in addition to the Bills and Giants, according to an NFL source.
McClain disclosed the Giants visit during his visit today and also told Buffalo reporters that he's not necessarily in a rush to sign with a team and will weigh his options carefully.
When the Ravens cut McClain, who recorded 52 tackles and one forced fumble in 10 starts last season after being activated from the reserve-physically unable to perform list once he recovered from a spinal cord contusion, they said they haven't ruled out potentially bringing him back.
At this point, though, there's been no movement toward the Ravens re-signing McClain, according to sources.