The right-hander allowed just two hits and walked one as Chicago won on opening day for the first time since 2009. Anthony Rizzo hit a two-run homer and Wellington Castillo added an RBI double for the Cubs.
Kyuji Fujikawa got a save in his major league debut after closer Carlos Marmol struggled.
A.J. Burnett, making the first opening day start of his lengthy career, gave up three runs on six hits in 5 2-3 innings, striking out 10. Pittsburgh however began a season of high expectations with a thud.
Burnett called it an honor to get the call in the opener, but the 15-year veteran showed some nerves early. Castro singled with one out and Rizzo followed with a towering two-run shot to center field that landed on the concourse behind the seats for one of the longest homers in the park's 13-year history. The ball left the park so fast even center fielder Andrew McCutchen — a Gold Glove winner last year — trotted only couple of steps before stopping.
Rizzo hit just .229 in spring training with just three extra base hits, but his blast gave the rebuilding Cubs an early shot of adrenaline.
Chicago threatened to expand the lead in the fourth, putting runners in scoring position with no outs. Two strikeouts and a harmless chopper to third ended the threat, but the Pirates could muster little fight against Samardzija.
It continued a troubling trend at home for the Pirates when Burnett takes the mound. Pittsburgh failed to score a single run in Burnett's final three starts at PNC Park in 2012, part of a miserable collapse that sent the ballclub to its 20th straight losing season.
Burnett couldn't even catch a break while attempting to keep his pitching hand dry. The rosin bag literally exploded while he was tapping it against his hip during the top of the fifth, showering the back of the pitcher's mound and Burnett's leg with dust.
Pittsburgh's offense was just as faulty against Samardzija.