Geary is based at TIME's international headquarters in London, and reports to editor Eric Pooley.
Formerly senior editor, Geary has been promoted to a re-created role, following recent editorial staff changes.
Pooley replaced husband and wife team Ann and Donald Morrison at the end of September, when they left to return to the US.
The deputy role existed prior to the Morrison's reign, but their co-editorship arrangement made the position unnecessary until now, explained Geary.
As deputy editor Geary will continue to oversee political coverage, and will take on enhanced editorial as well as managerial responsibilities.
He will initiate and extend coverage into regions covered less often in the past.