The essay was removed from the CBS Web site and an editor's note was posted saying the item should have credited Jeffrey Zaslow of the Journal, the network said Tuesday.
CBS would not identify the producer fired for the transgression.
The essays are carried regularly on "Couric & Co.," the anchor's blog on the CBS News Web site. Couric and producers meet once a week to decide on topics and the producers write them for Couric to read on camera.
An editor for The Wall Street Journal called CBS News to point out the similarities of the April 4 notebook item to Zaslow's article, headlined "Of the Places You'll Go, Is the Library Still One of Them?" The pieces talk about how libraries are seen differently by children from their parents.
"We were horrified," CBS News spokeswoman Sandra Genelius said. "It was almost verbatim."