Schwarber attended Middletown High School in Middletown, Ohio. During his four years, he hit .408 with 18 home runs and 103 RBIs.
As a freshman at Indiana University, Schwarber was named a freshman All-American by Louisville Slugger and Collegiate Baseball Newspaper after hitting .300/.390/.513 with eight home runs and 47 runs batted in. As a sophomore in 2013, he hit .366/.456/.647 with 18 home runs and 54 RBI in 61 games. He was named a first-team All-American by the National Collegiate Baseball Writers Association (NCBWA) After the season, Schwarber played for the United States collegiate national team during the summer. As a junior, he batted .348/.456/.643 with 13 home runs. He was a finalist for the Johnny Bench Award.
Schwarber was drafted by the Chicago Cubs in the first round, fourth overall, in the 2014 Major League Baseball draft. He signed on June 11. Upon being drafted, MLB.com analyst Bernie Pleskoff profiled Schwarber as a "game-changing" power-hitter. However, Pleskoff was critical of his base-running and fielding skills, commenting "Schwarber is sluggish on the bases and slow defensively". ESPN's Keith Law echoed a similar sentiment in his draft profile, noting "Schwarber might have the most raw power of any prospect in the class." Two pre-draft scouting reports by the MLB Scouting Bureau compared Schwarber's swinging mechanics to those of Jeff Bagwell, while also projecting him to play a role similar to Matt Stairs.
He made his professional debut with the Boise Hawks three days later, going 3-4 with a home run and three RBIs. The Cubs then promoted him to the Kane County Cougars of the Class A Midwest League and the Daytona Cubs of the Class A-Advanced Florida State League before the end of the season. Schwarber began the 2015 season with the Double-A Tennessee Smokies of the Southern League. In July 2015, he played in the All-Star Futures Game, where he was named the MVP of the game after hitting a go-ahead two-run triple for Team USA.
The Cubs promoted Schwarber to the major leagues on June 16, 2015, to serve as a designated hitter for six games during interleague play. Schwarber made his major league debut as a position player that night, replacing ejected starting catcher Miguel Montero in the eighth inning against the Cleveland Indians. The following night, as a designated hitter, he got four hits in five at bats with two RBIs and six total bases. The Cubs sent Schwarber to the Triple-A Iowa Cubs of the Pacific Coast League after the six games. On July 16, 2015, Schwarber was recalled from Triple A Iowa, to rejoin the Cubs due to an injury to catcher Montero. On July 21, in a 5–4 extra-inning victory over the Cincinnati Reds, Schwarber hit a game-tying 2-run homer in the ninth inning and a solo go-ahead home run in the top of the 13th to give the Cubs the lead. Schwarber's three multihomer games are the most for a Cub rookie in his first 51 games played since 1914. Over the course of the season he split time between catcher and outfield positions. He finished the 2015 regular season having played 69 games, recording a .246 batting average with 16 home runs, 52 runs scored, and 43 RBIs in just 273 plate arrearances. In the National League Wild Card Game, Schwarber drove in three runs and hit a long two-run home run to help the Cubs defeat the Pittsburgh Pirates, 4–0, and advance to the Division Series against the St. Louis Cardinals. In the NLDS, Schwarber helped the Cubs to a 3-1 series victory with 2 home runs, including a mammoth game 4 shot that landed on top of the new Wrigley Field scoreboard in right field. The ball was removed during the 2015-16 off season to prevent theft but was encased in Plexiglas and returned "to where it landed". In his eighth career postseason game, a 5-2 loss to the New York Mets in game 3 of the 2015 National League Championship Series (NLCS), Schwarber set a Cubs record with his fifth career postseason home run and also the record for the most home runs in a single postseason by a player age 22 or younger, passing Miguel Cabrera.
Schwarber only played two games before he was involved in an outfield collision with teammate Dexter Fowler on April 7, 2016, and was removed from the game with a left leg injury. Schwarber tore the anterior cruciate ligament and lateral collateral ligament in his left knee, and would miss the rest of the 2016 season. Despite being injured, there were many trade rumors surrounding Schwarber during the season, especially regarding the Cubs desire for a premium reliever. Club president Theo Epstein addressed Schwarber's situation by saying it "wouldn't be right to trade him". The Cubs eventually acquired closer Aroldis Chapman from the New York Yankees without having to give up Schwarber. As the Cubs advanced further into the postseason, an unexpectedly fast recovery made the return of Schwarber increasingly more of a possibility. Schwarber participated in a successful on-field workout with the team at Dodger Stadium before Game 3 of the 2016 NLCS. On October 22, Schwarber went to the Arizona Fall League to play with the Mesa Solar Sox, the same day the Cubs played in Game 6 of the NLCS.
The Cubs added Schwarber to their roster for the 2016 World Series, and started him in Game 1 as their designated hitter. Schwarber's addition to the Cubs' starting line-up was surprising given he had not played in a Major League game since his injury in April. Schwarber hit a double off the right-field wall in the 4th inning of Game 1. He became the first major league position player in baseball history to get his first hit of the season during the World Series. He was not medically cleared to play on defense, and only made appearances as a pinch or designated hitter. Schwarber and the Cubs defeated the Indians in seven games to claim the Cubs' first World Series championship in 108 years. During the World Series, Schwarber recorded seven hits, including one double, two RBIs, and one stolen base while batting for a .412 batting average and maintaining a .500 on-base percentage.
Schwarber was the opening day starting left fielder and lead-off hitter during April and May for the 2017 Chicago Cubs season. Schwarber started the first third of the year with one of the worst batting averages in all of baseball, hitting just .120 for the month of May. When he was demoted to Triple-A on June 22 he had 12 home runs and 28 RBIs but his batting average was the lowest in baseball, he was averaging a strike out every three at bats and was hitting just .143 against left-handers. Schwarber returned to the Cubs active roster on July 6, after the All-Star break. By August 12, he had hit safely in 10 of 13 games with five home runs, three doubles and a triple. He had struck out 106 times in 300 plate appearances.
Kyle is the son of Greg, a retired police chief, and Donna Schwarber. He has three sisters. Kyle's uncle Thomas Schwarber played college baseball as a pitcher at Ohio State and played professionally in the Detroit Tigers minor league system for three seasons from 1991 to 1993. Kyle played football as a linebacker in high school and also participated in Middletown High School's show choir.