HONG KONG—When a Canadian patent-licensing firm wanted to sue Japanese electronics company Sony Corp., it chose an unlikely venue: China.

Ottawa-based WiLAN Inc., which earns revenue by licensing its patents, filed a suit against Sony last week in a court in the eastern Chinese city of Nanjing, alleging that the Japanese company’s smartphones violated its wireless-communication-technology patent, according to the filing reviewed by The Wall Street Journal.

WiLAN’s...