Is sign stealing illegal in baseball? What MLB & Little League rules say about controversial tactic

Major League Baseball has featured many kinds of scandals in its existence, but very few are more unique to the sport than sign stealing.

Ever since baseball's inception in the late 1800s, teams have had paranoia regarding sign stealing and losing a competitive edge. That has only grown over time, as the game continues to introduce new technology over the years.

While the game will continue to evolve, sign stealing will always have a place in the game. Here's a breakdown of sign stealing and the differences between what's legal and what's illegal.

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What is sign stealing in baseball?

Sign stealing is when one team decodes the opposing team's pitching signs, allowing the hitters to know which pitches are coming. It gives the offense an advantage over the pitcher, taking away the pitcher's element of surprise.

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Is sign stealing illegal in baseball?

Sign stealing is legal in baseball under certain guidelines, and illegal under others. Players are allowed to steal signs on the field as long as it is natural, and they don't use any technology or other added elements to help them steal signs.

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MLB sign stealing rules

In Major League Baseball, stealing signs is legal but stealing signs using technology is illegal. So, baserunners are allowed to try and steal signs in games, but teams cannot use video devices in any way to decode the opposing team's signs.

After the Astros sign stealing scandal in 2017, MLB tightened its sign stealing rules by forbidding teams from installing cameras that can see catchers' signs. The league also initially banned in-game video, only to allow it to return in 2021 as long as the video doesn't include the catcher relaying signs.

Finally, club personnel who aren't participating in the game can't relay signs to players in any way.

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Little League sign stealing rules

Stealing signs is technically illegal in Little League. According to the Little League rules, umpires are able to eject any coach or player for stealing signs during a game.

"Each umpire has authority to disqualify any player, coach, manager or substitute for objecting to decisions or for unsportsmanlike conduct or language and to eject such disqualified person from the playing field. If an umpire disqualifies a player while a play is in progress, the disqualification shall not take effect until no further action is possible in that play. The stealing and relaying of signs to alert the batter of pitch selection and/or location is unsportsmanlike behavior."

At first, teams will be warned for sign stealing, but umpires then can disqualify coaches or players for offenses beyond the first act.

"If, in the judgment of the umpire this behavior is occurring, the team manager and those responsible including any player(s) and/or coach(es) shall be warned after the first offense. Those responsible including any player(s), coach(es), and/or manager shall be ejected from the game for a team’s subsequent offense."

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Most infamous sign stealing scandals in baseball

There have been many instances of sign-stealing accusations in MLB history. Here are a few of the biggest scandals in MLB history.

Hartford Dark Blues, 1876

The first known instance of sign stealing, according to "The Cheater's Guide to Baseball," belongs to the Hartford Dark Blues, who put a man in a small shack on a telegraph pole past the outfield wall to tell the hitter when a curveball was coming. 

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Philadelphia Phillies, 1900

In 1900, the Phillies executed sign stealing using technology for the first time, when backup catcher Morgan Murphy stole signs in an observatory over the center field wall. He would then notify the third base coach through a junction box that was connected to the observatory with an underground wire.

Murphy had other sign stealing systems for the team, like adjusting the awning on his observatory perch to sitting on rooftops, bleachers or buildings with newspapers on the road. 

New York Giants 1951

The 1951 Giants are responsible for one of the most iconic moments in baseball history, when Bobby Thompson hit the "Shot Heard 'Round the World" against the Brooklyn Dodgers to win the pennant. However, years later, several Giants players revealed the team was stealing signs.

"Every hitter knew what was coming," pitcher Al Gettel said in 2001, via The Wall Street Journal. "Made a big difference."

The Giants' penchant for sign stealing appeared to start with manager Leo Durocher.

"He asked each person if he wanted the sign," left fielder Monte Irvin, the Giants said. "I told him no. He said, 'You mean to tell me, if a fat fastball is coming, you don't want to know?'"

The Giants had an electrician named Abe Chadwick install a "bell-and-buzzer" system in the stadium that connected phones in the dugout and bullpen and allowed players in an office over center field to steal signs, using a Wollensak telescope, and buzz the bullpen, who would then relay the signs to hitters.

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Houston Astros, 2017

The Astros executed the biggest sign stealing scandal of the 21st century, as they were caught illegally stealing signs during their World Series championship season in 2017. While there was rampant speculation throughout the league about illegal sign-stealing Houston was caught using a center field camera to decode signs, then banging a trash can in the dugout to relay the findings to hitters.

MLB investigated the Astros after the 2019 season, in which Houston went to Game 7 of the World Series again, and the league fined the team $5 million and suspended manager A.J. Hinch and general manager Jeff Lunhow for the 2020 season. Houston ultimately fired both Hinch and Lunhow anyway, and Boston did the same with Cora but re-hired him a year later. Alex Cora and Carlos Beltran also lost their respective managerial jobs for their roles in the scandal, but Cora was re-hired a year later.

Boston Red Sox, 2017-2018

The late-2010s featured a lot of paranoia about sign stealing, and the Red Sox were one team that was caught. In 2017, Boston was fined for using apple watches to relay stolen signs against the Yankees, and in 2018 the team was fined for using the video replay room to steal signs.

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How MLB teams avoid sign stealing

As sign stealing became more prominent in Major League Baseball teams and players created ways to protect themselves. Catchers would often change pitch sequences with runners on base, and teams would use mound visits to directly speak to pitchers instead of using signs.

Most recently, teams adopted PitchCom, an electronic system that relays signs from catcher to pitcher without putting fingers down. One of the catcher-pitcher combination presses a button to choose a pitch, and the other end hears the selection through a device in their hat.

— Foul Territory (@FoulTerritoryTV) June 27, 2025