It happened about noon in the area of the 19000 block of Highway 530 between Whitehorse Trail and Ramstad Road, officials said.
The woman was flown via medical helicopter to Harborview Medical Center in Seattle, Oso Fire Chief Willy Harper said. She appeared to be alert and conscious at the time.
Arlington Fire Department medics and Snohomish County sheriff's deputies also were called to the scene.
The tractor was being driven by a 51-year-old Arlington-area man, sheriff's spokeswoman Shari Ireton said.
Deputies believe the incident was an accident, she said. There was no evidence of a crime.
View Tractor accident, 4-30-13 in a larger map
More Local News Headlines
Driver wipes out 5 cars at Everett repair shop Former county ombudsman John Koster files $950K claim Dream shared on social media prompts EvCC to boost security 9:20 a.m. Tulalip Tribes give nonprofits $5.8M in 'Raising Hands' initiative Lawmakers seek input on education funding in Everett on Tuesday Cascade senior wants to expand her interests in robotics Audit: City of Snohomish over-claimed $125K for roundabout costs Arlington thrift shop gives special-needs kids real-world skills
Our new comment system is not supported in IE 7. Please upgrade your browser here.