The sign, written in Italian, warns that people who violate the "no whining" policy are "subject to a syndrome of always feeling like a victim and the consequent reduction of your sense of humor and capacity to solve problems," according to Reuters.
It also says the penalty is double for people who gripe in the presence of children.
"To get the best out of yourself, concentrate on your potential and not on your limitations," the sign states. "Stop complaining and take steps to improve your life."
Motivational speaker Salvo Noé presented the pope with the sign last month, reports Vatican Insider, which first posted the image of it.
The pope has repeatedly spoken out against complaining, at one point warning that Christians who whine too much "have more in common with pickled peppers than the joy of having a beautiful life," according to Crux.