Backyard chickens in SeaTac, Washington

Yes. Backyard chickens are legal in SeaTac under SeaTac Municipal Code § 15.440.100, "Domestic Animals – Limitations", which is part of the City's Zoning Code (Chapter 15.440, Keeping of Animals). The code states that domestic animals are "permitted outright in all zone classifications within the City," and includes a specific table of outdoor animal limits by lot size.

Under that table, chickens (including roosters) are capped at five (5) birds per property, and this limit applies uniformly regardless of lot size — unlike dogs, cats, goats, and other animals whose limits scale up on larger lots. The five-chicken cap is also counted against the overall "Total Number of Outside Animals Allowed" for the lot (5–8 total animals depending on lot size), so other pets on the property can reduce how many chickens are actually permitted.

SeaTac sits in the mild, wet Puget Sound lowlands near Sea-Tac International Airport. Winters are cool and rainy but rarely see hard freezes, while summers are mild and dry. Flocks need good drainage and ventilation in coops to manage near-constant damp conditions from fall through spring, along with shade and ventilation for the drier, occasionally warm summer stretch.

Even in this urbanized, airport-adjacent city, wooded greenbelts and residential buffers host raccoons, opossums, and skunks that are skilled nighttime coop raiders, while red-tailed hawks and other raptors pose a daytime threat to free-ranging birds. Coyotes are also increasingly reported in King County suburban neighborhoods, so secure, covered runs and hardware-cloth (not chicken-wire) enclosures are strongly recommended.