In 1999, Sierra Leone is ravaged in a civil war. Rebel factions such as the Revolutionary United Front (RUF) frequently terrorize the countryside, intimidating Mende locals and enslaving many to harvest diamonds, which fund their increasingly successful war effort. Solomon Vandy, a local fisherman from Shenge, is captured. While his family escapes, Vandy is assigned to a workforce overseen by Captain Poison, a ruthless warlord.
While mining a river, Vandy discovers an enormous pink diamond. Captain Poison attempts to take the stone, but government troops raid the area. Vandy buries the stone before being captured. Both Vandy and Poison are incarcerated in the Sierra Leone capital of Freetown, along with Danny Archer, a Rhodesian smuggler and mercenary who was caught smuggling diamonds into Liberia. The diamonds were intended for Rudolph van de Kaap, a corrupt South African mining executive and a major player in the international diamond industry.
When Archer hears about the pink diamond, he arranges for himself and Vandy to be freed from detention. He travels to Cape Town to meet his employer, Colonel Coetzee, an Afrikaner formerly with the apartheid-era South African Defence Force. He now commands a private military company. Archer wants to sell the diamond so he can leave the continent forever, but Coetzee wants it as compensation for Archer's botched smuggling mission. Archer returns to Sierra Leone, locates Vandy, and offers to help him find his family if he helps recover the diamond.
Meanwhile, RUF insurgents escalate hostilities. Freetown falls and Vandy's son, Dia, is conscripted as a child soldier under a liberated Captain Poison. Archer and Vandy narrowly escape to Lungi, where Vandy is reunited with his wife and daughters in a refugee camp. He learns the RUF took his son. Vandy and Archer plan to reach Kono where Vandy buried the diamond. They are joined by Maddy Bowen, an American journalist who is working on an exposé of the illicit diamond trade. In exchange for Bowen's help, Archer promises to provide her the evidence she needs for her story.
Archer and Vandy, disguised as television journalists, travel with Bowen and a press convoy destined for Kono. Rebels ambush the convoy, forcing the three to flee. While trekking through the jungle, they encounter Kamajor militiamen, who take them to a friendly local named Benjamin Kapanay. The kindhearted Kapanay drives them to Kono, but an RUF child soldier injures him while en route. The trio arrive in Kono after a harrowing journey, where Coetzee and his private army—contracted by the Sierra Leone government—prepare to repulse the rebel offensive.
Archer gives Bowen the evidence and forces her to evacuate the country with other civilians; Archer and Vandy, having stolen weapons and supplies from Colonel Coetzee's army, set out for Captain Poison's encampment to retrieve the diamond. Along the way, the two men argue over what is the ultimate goal: Archer wants the diamond, while Vandy only wants to find his son.
At the encampment, Archer, seeing they are heavily outnumbered, calls Coetzee's army via satellite phone to request an airstrike. Vandy, desperate to find his son, sneaks into the encampment and locates Dia; due to Dia's brainwashing, he refuses to acknowledge his father. Vandy is captured but escapes when Coetzee's army arrives. Vandy finds and kills Captain Poison as the mercenaries overwhelm the RUF defenders. Coetzee takes Dia hostage and forces Vandy to produce the diamond, but Archer kills Coetzee after realizing the colonel will eventually kill them both. Dia briefly holds the pair at gunpoint, but Vandy is able to talk him down by reminding him of who he was. Pursued by vengeful mercenaries, Archer is mortally wounded. He entrusts the stone to Vandy, telling him to take it for his family. Vandy and his son rendezvous with Archer's pilot, who flies them to safety while Archer makes a final phone call to Bowen, in Cape Town; Archer asks Bowen to assist Vandy and his family, and gives permission for Maddy to finish her article before dying.
Vandy and Bowen meet in London, where they execute an undercover operation to expose the van de Kaap operation's dirty dealings. Vandy exchanges the pink diamond for 2 million pounds and a reunion with his entire family. Bowen publishes her exposé on the diamond trade and van de Kaap's criminal actions. Later, Vandy appears as a guest speaker at a conference on blood diamonds in Kimberley, where he is met with a standing ovation.
Leonardo DiCaprio as Daniel "Danny" Archer
Djimon Hounsou as Solomon Vandy
Jennifer Connelly as Maddy Bowen
Kagiso Kuypers as Dia Vandy
Arnold Vosloo as Colonel Coetzee
Antony Coleman as Cordell Brown
Benu Mabhena as Jassie Vandy
Anointing Lukola as N'Yanda Vandy
David Harewood as Captain "Poison"
Basil Wallace as Benjamin Kapanay
Jimi Mistry as Nabil
Michael Sheen as Rupert Simmons
Marius Weyers as Rudolf van de Kaap
Jonathan Pienaar as journalist
Stephen Collins as Ambassador Walker
Ntare Mwine as M'Ed
Ato Essandoh as Commander Rambo
Tony Kgoroge as Troop Leader