The accident happened around 5 p.m. when police say she tried crossing the Belt Hwy. just north of Frederick Ave.
Police say she was trying to cross from Heartland Urgent Care Clinic to Walgreens where there was no crosswalk.
"She cleared the northbound lanes," said officer Brendan McGinnis with the St. Joseph Police Department. "When she got to the southbound lanes of the Belt Highway a vehicle stopped to let her pass probably due to the weather. The outside lane truck did not see her crossing and eventually struck her."
The woman's name has not yet been released. Police continue to investigate.