Yvonne Anderson was last seen at the Sunrise North Senior Living Residence, on Burnhamthorpe Road E. near Dixie Road, around 5:30 p.m. on Friday.
Police said in a news release that Anderson recently moved to the facility and they are concerned she may be "confused" about where she lives.
She is familiar with both the Mississauga and Toronto transit systems, police said.
Anderson is described as black, 5'4 and around 155 pounds. Police said she wears glasses and was last spotted wearing a grey jacket.