Under the rule, one free throw will be awarded for any foul that would typically result in one, two or three free throws under current NBA rules.
That free throw would be worth the same total number of points as the free throws it replaces.
During the final two minutes of the fourth quarter and overtime, standard free throw rules will be in effect.
The one free throw rule has been used in the developmental G League since the 2019-20 season to "improve game flow."
It's not clear if the rule could eventually be used in the NBA proper, although previous tweaks, including coaches' challenges, have been tested in the G League and Summer Leagues before they were adopted.
Summer League play, in which all 30 teams field rosters of rookies, second-year players and G-League prospects, will take place July 3rd to 19th.
The California Classic Summer League runs from Friday through Monday in San Francisco and Sacramento with seven teams taking part.
Four teams will take part in the Salt Lake City Summer League on Saturday through Tuesday, and all 30 teams will field teams in the Las Vegas Summer League July 9th to 19th.
This year's contests will also use a "connected" basketball with an embedded sensor. The NBA says the ball will provide data to support future officiating applications such as last-touch out-of-bounds calls.