The Yes Man star confirmed the pair's engagement back in April (09), after two years of dating.
Deschanel is currently filming forthcoming movie Your Highness in Northern Ireland - but is planning to return to the U.S. later this month for an autumn wedding.
A source tells New York Post's gossip column PageSix, "Zooey is in Belfast with James Franco and Natalie Portman but will return at the end of September for her ceremony in Seattle."