The novel’s title, Full of Beans, is both an idiomatic phrase for not speaking truthfully and an indicator of the theme of deceit and distrust. Beans starts his narrative by asserting that adults lie frequently and carelessly; the opening scene when Winky reneges on a promised payout is a case in point, as well as later when Poppy smoothly covers the fact that he is thinking of moving the family to New Jersey. Beans feels so certainly that grown-ups lie all the time that when Mr. Stone arrives and describes his position as a representative of President Roosevelt, Beans replies, “Course I believe you, mister […]. Why, we just had the Queen of England visit here last week” (9). Another example of an untrustworthy character is Johnny Cakes; his strongest characteristic is his ability to deceive. Many regard him as a criminal, and Beans soon learns that the liquor Johnny Cakes runs to businesses from Cuba is not legal.

Other characters whose honesty readers may debate include Dot and Nana Philly. Dot lies flatly to Beans when he asks her if the pineapple shipment is in, causing him to miss the treat.