"In the treacherous and swampy forests that make up the so-called 'green border' between Belarus and Poland, refugees from the Middle East and Africa trying to reach the European Union are caught in a geopolitical crisis triggered by Belarusian dictator Alexander Lukashenko.

Pawns in this hidden war, the lives of Julia, a newly minted activist who has given up her comfortable life, Jan, a young border guard, and a Syrian refugee family intertwine.

[8] Holland made the decision to begin work on the film in September 2021;[10] she and her two fellow screenwriters, Maciej Pisuk and Gabriela Łazarkiewicz-Sieczko,[9] "documented [the border crisis] very deeply" when writing the screenplay,[10] with this research including hundreds of hours of document analysis and of interviews with refugees, borderland residents, activists and experts,[8] as well as testimony by anonymous Polish Border Guard officers.

It was decided that the film would be shot in black-and-white as it was thought that to do so would be "metaphorical, and somehow connected to the past, the Second World War, documentary-like", in addition to allowing for better visual and artistic control considering the shooting and editing schedule.

Agnieszka Holland retorted that Law and Justice ended up losing local elections in Ostrołęka after that city's council acted similarly to prevent screenings of Kler.

The idea of a school trip to see the film was originally that of Marzanna Gądek-Radwanowska, a teacher at the liceum who also happened to be a Civic Platform candidate in the then-upcoming parliamentary election.

"[30] Leslie Felperin of The Hollywood Reporter hailed the execution and precision of the film's multiple storylines, which she wrote "make for a bracing, impassioned skein of humanist cinema, old-school in technique but right up to the moment in terms of its subject matter.

"[31] Screen International's Wendy Ide echoed praise of the film's "supremely confident handling of a fractured, fragmented structure and its twin driving forces of compassion and fury.

"[32] In a less favourable review, Kevin Maher of The Times acknowledged the film as "expertly made, and harrowing", but criticized its dialogue as "podium-speak, ramming manifestos into the mouths of characters and transforming every scene into a Manichean struggle between the forces of darkness and light."

Maher ultimately panned the film as being nothing more than misery porn, lacking the nuance of other modern refugee dramas such as For Sama (2019), Flee (2021) and Tori and Lokita (2022).

[33] Green Border was consistently criticised by ministers from the Law and Justice-led Second Cabinet of Mateusz Morawiecki: Holland responded to Ziobro's comments by saying that the government was afraid of her film's depiction of the crisis.

"[21] Gazeta Wyborcza published an open letter with over 500 signatories condemning the attacks by public officials and expressing full solidarity with Holland.

The authors of the press release claimed that to distribute the film was to incur "disgrace and the deepest contempt" and, in criticising Holland's portrayal of engineers, doctors, and writers being among the migrants, challenged her to tell Border Guard officers that the thrown objects they were being attacked with were merely "calipers, stethoscopes, and pen nibs".

[12] According to Kino Świat, Green Border was seen by over 137,000 people during its opening weekend; this would be a record result for Polish films that premiered in their home country during 2023.

[57] In the weeks leading up to the film's release, pro-government and nationalist individuals organised a review bombing campaign on Filmweb; out of 78 ratings on the site as of 6 September 2023, the average score was just 2.0 out of a possible 10.