Peter Austin, managing director for London Overground Rail Operations Limited (LOROL), said:
"We are disappointed by the result of the ballot, but would highlight that fewer than half of our 124 conductors voted, and only 43% of those voted in favour of industrial action.
"We believe industrial action is unnecessary. LOROL continues to give the RMT assurances on employing conductors in alternative customer service roles and offering a generous voluntary redundancy package to those who want it.
"We urge the RMT to work with us to maintain progress in safeguarding jobs and avoid disruption to passengers."