A device for conveniently and safely harnessing a pet to a standard seat belt receiver of a vehicle. The device includes a latching member that configured to be received and latched into a standard seatbelt receiver of a vehicle. The latching member can be pivotally connected with a housing so that it can be pivoted outward for attachment to the seatbelt receiver and pivoted back in when not in use. The device also includes a leash re-wind mechanism that maintains a constant tension on the leash during normal use and that locks extension of the leash when a sudden, abrupt extension of the leash occurs.