Stanislaw Michalek, who came to Washington from the Archdiocese of Poznan in Poland, blessed the plane with holy water during the ceremony at Everett's Paine Field.
Poland's LOT was Europe's first airline to purchase the new model with an order for eight. It plans to fly its first Boeing 787 on short-haul flights in December in Europe. Early next year it will fly routes between Poland and New York, Chicago and Toronto.
It was the 35th 787 Boeing has delivered overall, and 803 more are on order.
Boeing says the 787 is the first mid-size plane capable of flying long-range routes, allowing airlines to open new, non-stop flights.