Millwood is located at 47°40'51" North, 117°16'54" West (47.681111, -117.281667).
According to the United States Census Bureau, the town has a total area of 0.72 mi2 (1.87 km2). 0.69 mi2 (1.78 km2) of it is land and 0.03 mi2 (0.09 km2) of it is covered by water. The total area is 4.77% water.
Millwood is located in the Pacific Standard Time (PST) timezone, GMT-08:00. It observes Daylight Saving Time (DST).