The following two years he pitched for Israel in the qualifying for the European Baseball Championship, and won the Most Valuable Pitcher award in both 2014 and 2015.

Kremer pitched for San Joaquin Delta College in his freshman year in 2014, and was named a Third Team All-American.

He threw a fastball in the 92–95 mph range that sometimes reached 97 miles per hour (156 km/h), a slider, a curveball, and a splitter.

[5] His parents Adi and Sigal Kremer are Israeli, and after they completed their service in the Israel Defense Forces they came together to the United States.

[20] He had been projected to go much higher in the draft, but for the fact that he had already committed to the University of Nevada, Las Vegas, and told interested MLB teams that he intended to attend the school for a year.

[21][7][22] In the 2016 Major League Baseball draft, Kremer was picked in the 14th round by the Los Angeles Dodgers, 431st overall.

[18][19] Kremer made his professional debut on July 3, 2016, for the Ogden Raptors of the Rookie Pioneer League.

[4] Kremer finished his first professional regular season between the two teams with a 2–1 record and a 2.27 ERA, as in 31.2 innings he struck out 35 batters, while giving up 19 hits and 7 walks while holding hitters to a .176 batting average.

[1][27] In the playoffs, Kremer pitched 10.1 innings with an 0.87 ERA and 6 strikeouts, and recorded the final eight outs of the Loons' championship-clinching win over the Clinton LumberKings.

[28] The Dodgers assigned Kremer to the Rancho Cucamonga Quakes of the Class A+ California League for the 2017 season.

There he made 33 appearances for the team (including six starts), was 1–4 with three saves and a 5.18 ERA, and struck out 96 batters in 80 innings.

[33] On July 18, 2018, Kremer was traded to the Baltimore Orioles along with Yusniel Diaz, Rylan Bannon, Zach Pop, and Breyvic Valera for Manny Machado.

[34] At the time, FanGraphs wrote of Kremer: "Throws 92–95, touches 97, above-average curveball, average change.

In 2018 in 25 starts between Rancho Cucamonga, Tulsa, and Bowie, he was 10–5 with a 2.88 ERA, striking out 178 batters (leading the entire minor leagues) in 131.1 innings pitched.

[38] He was a combined 9–6 with a 3.72 ERA, as in 113.2 innings he struck out 122 batters, averaging 9.7 K/9, 2.9 BB/9, 0.87 HR/9, and a ground-ball rate just short of 40 percent.

He was named a league All Star, and was added to the Orioles' 40 man roster to protect him from being claimed in the Rule 5 draft.

[50] Kremer made more history by becoming just the second rookie to—in each of his first three starts—throw at least five innings, with one or no runs, four or fewer hits, and at least six strikeouts; Eduardo Rodriguez of the Boston Red Sox is the other pitcher to accomplish that feat.

[52] Before Kremer, the three prior Orioles with at least 18.2 scoreless innings in the span of three starts were Kevin Gausman, Fernando Valenzuela, and Jim Palmer.

[62] In the opening game against Finland, he went 5 innings, giving up 2 hits and 1 unearned run, and recording 9 strikeouts, while earning the win.

[63] He then pitched again during the semifinal game against Romania, going 8 innings, giving up 4 hits and 1 unearned run, and recording 5 strikeouts, while earning his second win of the qualifier.

Kremer again pitched on the opening day, going 6 innings against Belarus, not giving up any runs, striking out 10, and recording another win.

[65] During Israel's fifth and final game of the B-level qualifier, against Sweden, Kremer started again going 7.1 innings, giving up 4 runs (3 earned) and 9 hits, and striking out 5.

[69] Kremer pitched for Team Israel at the 2017 World Baseball Classic main tournament, in March 2017.