O'Conner signed a minor-league contract with the Giants which includes an invitation to spring training, Amy Gutierrez of NBC Sports Bay Area reports.
With Buster Posey and Nick Hundley set to return as the Giants' catching duo, O'Conner should spend 2018 on the farm as organizational catching depth. The 25-year-old split time with Triple-A Durham and Double-A Montgomery in 2017, hitting a .227/.288/.372 in a combined 85 games at both stops.