Mineo's Pizza House in Squirrel Hill opened its expanded section on Monday, which includes a full bar with 42 seats.
The restaurant is a third larger than when Giovanni "John" Mineo opened the place on Murray Avenue in 1958.
"We thought we'd shake things up by opening on St. Patrick's Day," said co-owner Dominic Mineo, whose family is originally from Sicily.
The expansion project took over space previously occupied by Engel's Market, which closed in April.
Mineo's has been serving beer and malt beverages for the past three years but no wine or spirits until now.
The owners have also added items on the menu, such as arancini and four types of wings: Buffalo-style, mango-jalapeno, barbecue and lemon rosemary.
Mineo's lore includes the defection of employee Giuseppe "Joe" Aiello, who left after 12 years to open Aiello's Pizza in 1978 -- a few paces up the block.
Since the split, Pittsburgh's pizza fans have remained polarized as each camp maintains devotion to one place or another.
Creator of the Facebook group "Mineo's or Aiello's?" explained the rivalry this way on the group's website when it debuted in 2009:
"Pittsburgh's a great town for many things -- count pizza among them. And Murray Avenue in Squirrel Hill may be the Mecca of Pittsburgh ZA. Taste buds are sophisticated, traditions run deep and emotions are high."