The film sees the actor recount the life and career of his late father, Robert Downey Sr., who passed away last year.
The documentary, which is due to be released globally on Netflix on December 2, has been playing in selected cinemas over the past week, and it has been acclaimed by critics during its initial run.
The Daily Beast's Nick Shager said the documentary was "infused with the unique humor and creativity of its subject, as well as steeped in the complicated but palpable love shared by a father and son", saying the affection felt between the pair was "moving in its sincerity and openness".
Despite liking the film overall, some reviews were less positive, with IGN Movies saying the film was more "informative than emotional", adding that it "contains hints of an intimate story, but mostly flattens a strange and exotic career into a series of light observation".
The film, which was shot over the course of three years, depicts the father-son relationship throughout their lives.
Earlier this month, the actor announced the project on his Instagram page, saying of his father: "He was a groundbreaking filmmaker. As well as my dad. It's not uncomplicated… Sr. is a documentary that tells the story of Robert Downey's maverick rise in NYC, his crash, burn and redemption in Hollywood and our relationship in the aftermath."
Sr. will be released on Netflix on December 2.
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