The Romney campaign said Ryan will appear at a morning rally in a private hangar by Pittsburgh International Airport. Tom Smith, the GOP candidate for U.S. Senate, will speak at the rally.
Ryan's visit comes just days after Romney's wife, Ann Romney, visited the traditional battleground state, which many political observers had viewed as out of reach for the Republican ticket. Recent polls have shown a much tighter race.
A Quinnipiac University poll released Tuesday found Romney now trails Democratic President Barack Obama by just 4 percentage points among likely Pennsylvania voters. The same pollster showed Obama with a 12-point lead in late September in the state.
Democrats outnumber Republicans in Pennsylvania by a 4-3 ratio and have won the last five contests for president in the state.
Pittsburgh is a strategically important area for the Republican Party. The city's media market reaches eastern Ohio, a primary battleground state, and heavily populated southwestern Pennsylvania is an area of growing strength for Republicans. Republicans hope to sway the area's conservative Reagan Democrats, who are turning away from Obama but have not fully embraced Romney.
In addition, a heavily contested race for U.S. House is being waged there by Republican lawyer Keith Rothfus and Democratic U.S. Rep. Mark Critz.
Pennsylvania is tied with Illinois for the nation's fifth-biggest electoral prize in the presidential election and historically has been treated as a battleground state. But practically all of the ads in the presidential race ceased in August in Pennsylvania, and visits by the presidential and vice presidential candidates have been few.
Ryan has visited Pennsylvania just once as the vice presidential candidate, on Aug. 21.
Obama hasn't campaigned in Pennsylvania since June, and Vice President Joe Biden, like Romney, last campaigned in the state in September.