Fans of the Mass Effect 3 will be offered a chance to find out more about the video game's ending, on 26 June.
Creator Bioware is releasing a free update that gives players more insight into the effect their actions had on the original game's setting.
The extended ending follows an outcry by fans who complained the original ignored decisions made during play.
European owners of the PlayStation 3 will have to wait until 3 July for a version for their console.
First released in 2007, the Mass Effect series has proved a hit largely because the decisions players make during the game change how it ends.
The third outing made more of this interactive element by letting players use saved games from the first two in the series as the last title's starting point.
In early 2012, players voiced their displeasure when the ending of Mass Effect 3 served up a conclusion that seemed to ignore that history.
Players banded together as the Retake Mass Effect campaign to lobby for an alternative ending. More than 4,000 of them donated $80,000 (£51,000) to the Child's Play charity as a way to show their annoyance.
This donation drive was shut down by Child's Play after it emerged many people thought they were giving money to produce a new ending for Mass Effect 3.
In response to the broader campaign, Bioware said it would produce an Extended Cut ending that would do more to show how a player's actions influenced the universe of Mass Effect 3.
"Through additional cinematic sequences and epilogue scenes, the Extended Cut will include deeper insight to Commander Shepard's journey based on player choices during the war against the Reapers," said Bioware on its website.
In an audio interview put on YouTube, Bioware producer Casey Hudson said the extended ending was needed to re-assure people that what they did in the game mattered.
In a comment that referred to the way the series ends he said: "In some cases, people feared the worst - that no matter what your decisions you make, the entire galaxy is destroyed, everyone starves to death and so on, which of course, wasn't our intention," he said.