At the time of the book's publication, Kirkus Reviews wrote "There may be a run on the Metropolitan (a map is provided); there will surely be a run on the book."[11] The Horn Book Magazine called the book "not only one of the most original stories of many years but one of the most humorous and one with character wholly alive."[12] In a retrospective essay about the Newbery Medal-winning books from 1966 to 1975, children's author John Rowe Townsend wrote "Mrs. Frankweiler plays a vital part, and has an important affinity with Claudia; it is quite likely that she herself is a Claudia grown elderly...Yet the fact that Mrs. Frankweiler narrates the whole story, which she herself does not enter until near the end, seems to me to be a major structural flaw."[13]
Mixed-Up Files won the annual Newbery Medal for excellence in American children's literature in 1968, and Konigsburg's first-published book Jennifer, Hecate, Macbeth, William McKinley, and Me, Elizabeth was one of the runners-up in the same year, the only double honor in Newbery history (from 1922).[4] Anita Silvey covered Mixed-Up Files as one of the 100 Best Books for Children in 2005.[14] Based on a 2007 online poll, the U.S. National Education Association listed it as one of its "Teachers' Top 100 Books for Children".[15] In 2012 it was ranked number seven among all-time children's novels in a survey published by School Library Journal.[16]
