The person spoke on condition of anonymity Wednesday night because the ban is among the details of the sport's new collective bargaining agreement that have not been announced.
The ban does not apply to any player who already has at least one day of major league service.
In addition, several cities have banned the use of smokeless tobacco in ballparks, including Boston; Chicago; Los Angeles; New York; San Francisco; and Washington, D.C. The Milwaukee City Council approved a ban last week.
In the minor leagues, where players are not unionized, smokeless tobacco has been banned since 1993.
As part of the 2012-16 labor agreement, the union agreed that players may not carry tobacco packages and tins in their back pockets when fans are permitted in the ballpark, and players may not use tobacco during pregame or postgame interviews, and at team functions.