Brooklyn once had a sizable Irish population and a long history of influential Irish politicians. The two neighborhoods in Brooklyn that still reflect the borough's Irish origins are Bay Ridge and the combined areas of Park Slope and Windsor Terrace.
Brooklyn's "Little Ireland," such as it is, is most visible along Bay Ridge's Third Avenue.
Many Irish pubs, some old timers, but mostly new establishments, are located in a stretch between about 84th Street and 95th Street on Third Avenue.
You can also find Irish specialty import shops, Irish newspapers, and a local St. Patrick's Day parade in full regalia that begins and ends in Bay Ridge.
Windsor Terrace & Park Slope
In the two adjacent neighborhoods of Windsor Terrace and Park Slope, several old-time Irish bars, notably the picturesque Farrell's, still hark back to the early 20th century when much of South Brooklyn was either Irish or Italian. (For better or worse, a number of old Irish bars, such as Snooky's on 7th Avenue, are long gone.)
Windsor Terrace was settled by Irish Catholics, and a centerpiece of the neighborhood is Bishop Ford High School.
Park Slope continues to have sufficient Irish energy to celebrate its long-standing local Park Slope St. Patrick's Day parade through the neighborhood, complete with kilt-wearing bagpipe players.
Not So Irish Anymore
Not one of these three areas—Bay Ridge, Windsor Terrace or Park Slope—are homogeneously Irish neighborhoods.
Once very Irish, Bay Ridge is today a polyglot area with a sizable immigrant population that's more likely to visit a mosque or halal food store on Friday than to down a Guinness. And, gentrification has diluted what's visibly Irish about most of South Brooklyn, including Park Slope and Windsor Terrace.
Still, many older Irish Americans live in these neighborhoods, as do some prominent local politicians of Irish ancestry. If you're looking for a "touch o' the Irish" in Brooklyn, then Bay Ridge, and to a lesser extent Windsor Terrace and Park Slope (and a few outstanding Irish pubs scattered throughout the borough) are your best bets.