MLB said that the suspension, which is without pay, is effective immediately.
In a statement accepting his suspension, Byrd said Wednesday that, in 2012, he was was using Tamoxifen "on the advice of a physician for a medical condition resulting from surgery, and I accepted my suspension without challenge."
"Since that time, I have paid close attention to the substances that are banned by the Joint Drug Agreement, as I had no intention of taking any banned substances. I relied upon a medical professional for assistance and advice with respect to the supplements that I was taking. However, certain supplements I was taking were not on the NSF Certified for Sport list, and therefore, I assumed certain risks in taking them.
"When I learned that I had tested positive for Ipamorelin, I retained the services of private counsel and an independent chemist to determine the origin of the Ipamorelin test result because I never knowingly ingested Ipamorelin. After an extensive investigation by my lawyers and an independent chemist, it was concluded that the most likely source of Ipamorelin was a tainted supplement.
"I alone am responsible for what I put in my body, and therefore, I have decided for forgo my right to an appeal in this matter and accept the suspension. I apologize for any harm this has caused the Cleveland Indians, Indians' fans, my teammates, and most importantly, my family."
Retired pitchers Dan Haren and Jeremy Guthrie, and Detroit Tigers right-hander Justin Verlander, who was outspoken about Miami Marlins second baseman Dee Gordon's suspension for PEDs, were among the players to react to the news on Twitter.
@Ken_Rosenthal can I get back all the home runs he hit off me please? Thanks— dan haren (@ithrow88) June 1, 2016
Also last year magically returned from a broken wrist in 16 days, at age 38. Proceeded to homer off me that day. https://t.co/7ubQOpskCk— dan haren (@ithrow88) June 1, 2016
Marlon Byrd is a joke. All you cheaters are a joke. Do it the right way one time, accept your ups & downs.— Jeremy Guthrie (@TheRealJGuts) June 1, 2016
Byrd packed his belongings following a loss to Texas on Tuesday night, but he didn't tell the team about his suspension until he called manager Terry Francona on Wednesday morning. Later, he spoke to his teammates as a group in Cleveland's clubhouse.
"Marlon stood up in front of everybody and took responsibility and apologized,'' Francona said. "And, basically, he told the guys that his career is over and this is not how he wanted it to end. I'm sure there's going to be a lot of criticism of the situation, but it doesn't take away that we care about him. We care about our team, but we also care about the individuals. So, that hurts.
"It feels like we got kicked in the stomach a little bit.''
Byrd, who signed a minor league contract with the Indians in spring training but made the major league team out of camp, is hitting .270 with five home runs and 19 RBIs in 115 at-bats this season.
He is the second Indians outfielder to receive a PED suspension this season. Abraham Almonte received an 80-game suspension before the season for the performance-enhancing drug Boldenone.
Almonte had been expected to get significant playing time to start this season while outfielder Michael Brantley was sidelined following shoulder surgery. Brantley made his debut on April 25 but was shut down again on May 14 because of his shoulder. He hit .231 with seven RBIs in 11 games this season, but there is no timetable for his return.
In roster moves after Byrd's suspension was announced, the Indians recalled outfielder Tyler Naquin from Triple-A Columbus and optioned right-hander Shawn Armstrong to the minors. The team also purchased left-hander Tom Gorzelanny's contract from Columbus to fill Byrd's roster spot.
Last season, splitting time between Cincinnati and San Francisco, Byrd batted a combined .247 with 23 home runs and 73 RBIs in 135 games.
A career .275 hitter, Byrd has connected for at least 20 homers and driven in 70 or more runs in each of the past three seasons. He batted .271 against left-handers and has a career .286 average against lefties.
Byrd began his career in 2002 with Philadelphia and finished fourth in voting for the 2003 National League Rookie of the Year. He has 159 career homers while playing for 10 teams during his 15-season career.
The Associated Press contributed to this report.