When Minato was in the Ninja Academy, his classmate and future wife Kushina Uzumaki thought he looked "flaky" and even "girly". He dreamed of being acknowledged by the Konoha villagers by becoming Hokage, which Kushina considered to be an impossible dream for someone like him. Years later however, when Kushina was kidnapped by Kumogakure ninja, Minato was the only one to pick up on the fact that she was leaving behind strands of her red hair to mark their path. After rescuing her, Minato explained that he had always admired her hair. No longer seeing him as "flaky", she fell in love with him.
According to those who knew him, Minato was a very talented ninja, having been considered a rare genius that appeared only once a generation. He graduated from the Ninja Academy at the age of ten, and was added to a genin team under the tutelage of Jiraiya. Jiraiya took a special interest in Minato, and accepted him as an apprentice, amongst other things teaching him the Summoning Technique. Jiraiya even believed Minato might be the Child of the Prophecy, someone who would someday save the world.
In time, Minato was put in charge of a genin team of his own, consisting of Rin, Obito Uchiha, and Kakashi Hatake. During the Third Shinobi World War, Minato led his team on a mission into Kusagakure to destroy the Kannabi Bridge. Because Kakashi had recently become a jōnin, Minato gave leadership of the mission to Kakashi while he went to help Konoha's forces on the front lines. After meeting up with the surviving and out-numbered Konoha ninja, Minato used his Flying Thunder God Technique to destroy the opposing Iwagakure ninja. He then returned to his team, just in time to save Kakashi and Rin from another group of Iwa forces; he was too late to save Obito. When Kakashi and Rin recovered from the ordeal, Minato helped them complete the mission.
At some point, he clashed with A multiple times. At their first meeting he recognised A's brother Killer B as the jinchūriki of the Eight-Tails. Upon receiving the signal that Konoha was retreating, he declared that they would later face each other to put the title of Kage on the line and also offered A the advise of making sure his brother knew who he was before becoming neither human nor jinchūriki.
When the war ended, Minato, not yet thirty years of age, was chosen to become the Fourth Hokage. At some point during his reign he read Jiraiya's first book. He liked the main character's determination, believing he was just like Jiraiya. Since Kushina was pregnant with their son, Minato informed Jiraiya that they planned to name their son "Naruto" in the hopes that he would be just like the main character and, in turn, Jiraiya. Jiraiya warned them that this would make him Naruto's godfather, but they insisted that this was a good thing.
Because Kushina was the jinchūriki of the Nine-Tailed Demon Fox, special arrangements had to be made for Naruto's birth. Since the seal keeping the Nine-Tails within her would weaken during childbirth, Naruto would secretly be delivered in a remote location outside Konoha. ANBU would guard the area and Minato would maintain the seal while Kushina went into labour. Soon after Naruto was born they were found by Madara Uchiha. Madara killed all of the ANBU and took Naruto hostage, threatening to do the same to him. Minato was able to take Naruto back, but this gave Madara the chance to escape with Kushina. Minato found a safe place to put Naruto and then teleported to Kushina. He arrived in time to stop the Nine-Tails, having been removed from her body, from killing her, and teleported back to Naruto. Minato reunited mother and son and then went to help defend Konoha from the Nine-Tails.
Minato arrived in the early stages of the Nine-Tails' attack. After protecting the village from its Tailed Beast Ball, Minato tried to reach the Third Hokage to inform him of what had happened. He was stopped by Madara, who tried to send him away. Minato escaped but was followed by Madara. When the two began fighting, Minato struggled to hit Madara, Madara being intangible whenever he was not currently attacking. By carefully timing his Flying Thunder God Technique, Minato was able to strike him during one of these rare moments and apply a seal for the Flying Thunder God Technique to him, allowing him to teleport to Madara whenever he wanted. He placed a Contract Seal on Madara to remove the Nine-Tails from his control, forcing Madara to flee.
When Minato returned to the village he found it in ruin. He summoned Gamabunta to distract the Nine-Tails long enough to teleport it away from the village to Naruto and Kushina's location. Kushina restrained it and, dying from the trauma of its removal, volunteered to have it sealed back into her body so that it would die with her. Distraught, Minato suggested instead using the Dead Demon Consuming Seal on the Nine-Tails to weaken it and then seal the rest into Naruto. Kushina objected since this would mean Minato's death and give Naruto a horrible, lonely life. Minato insisted it was for the best since allowing the Nine-Tails to resurrect itself, without a jinchūriki to contain it, would inevitably cause harm to Konoha and the Fire Country. Also, Minato was convinced that Naruto, the "Child of the Prophecy" Jiraiya had once told him about, would need the Nine-Tails' power to someday defeat Madara. After Minato used the Dead Demon Consuming Seal on it, the Nine-Tails realised their intentions and tried to kill Naruto, but Minato and Kushina used their bodies to shield him.
While Kushina gave a few finals words to Naruto, Minato summoned Gerotora, gave him the key to the seal he would use on Naruto, and sent him to Jiraiya. After Kushina told Naruto how much his parents loved him he seconds everything she says and then sealed the Nine-Tails and the rest of their chakra into Naruto so that they would be able to see him again when he was older, ending their lives. Since the Third Hokage had come to help, Minato used his last moments to request that Konoha think of Naruto as a hero, and not the container of the monster that caused so much death and destruction. Before he died he sealed his own chakra into Naruto so that he could someday see Naruto again too, specifically if ever the seal was about to break so that he could restore it.
The Third Hokage did his best to look out for Naruto but very few were willing to regard Naruto as anything but the Nine-Tails' jinchūriki. The Third Hokage forbade anyone from speaking of the Nine-Tails, hoping that those too young to remember the Nine-Tails' attack would not hate Naruto as the rest of the village had. He gave Naruto his mother's surname so that his relation to Minato would be kept a secret from Minato's enemies. He otherwise did his best to give Naruto a comfortable life despite Naruto having no parents and being made into an outcast by the rest of the village. Naruto would never be told his parents' identities, and neither would most of Konoha.
With Minato's death, the Third was forced to resume his position as Hokage, a role he filled until his death, never being able to find a replacement of Minato's calibre. Minato himself became regarded as the village's hero and, indeed, one of the greatest ninja Konoha had ever produced, so much so that villagers would regret his death whenever tragedy struck the village. Because Minato was never able to tell anyone what happened during the Nine-Tails' attack, villagers were forced to make their own explanations. Jiraiya recognised that Minato would not have sealed the Nine-Tails into his own son unless he had a good reason and that Minato intended Naruto to gain control of the Nine-Tails, but could never satisfactorily explain why.
Although Naruto had no idea about his relation with Minato most of his life, he appeared to greatly admire the Fourth Hokage, considering him a hero who gave his life for the village, showing anger when Tsunade spoke ill of him and becoming overjoyed whenever Jiraiya or Kakashi mentioned his resemblance with Minato. Before Naruto left Konoha to begin his training with Jiraiya, he looked at the Fourth Hokage's carved head and asked him to look after him. After learning the truth about his relation to Minato and despite the shock that his own father made him a jinchūriki, Naruto was proud to be the Fourth Hokage's son.
Years after his death, Killer B was surprised when he learned Minato created a technique similar to the Tailed Beast Ball, the Rasengan.