Marcello Di Finizio told Romereports.com that his protest wasn't against the Vatican but was instead against Italian Prime Minister Mario Monti, the European Union and the economic crisis.
Di Finizio hung a banner that read in part: "Help!!! No more Monti, no more Europe, no more multinationals" over a window on the dome, the Italian news agency ANSA reported.
He said he was also angry about a European Union directive that involves seaside bars like the one he owns in Trieste.
Vatican sources said Di Finizio had conversations with two government ministers Tuesday but neither was able to persuade him to come down.
Pope Benedict XVI was scheduled to give his weekly audience in St. Peter's Square Wednesday.