He was born into the Bovino Famiglia, a Mafia family, where he dreamed to become the boss of the Bovino Famiglia and take over the world. Lambo had befriended Reborn one day meeting him at a bar, where Lambo had a pleasant conversation with him, until it was revealed that Reborn had fallen alseep through the entire conversation, and turning Reborn into his enemy.
At the age of five, he left his birth family and travelled to Japan. The Bovino Famiglia's boss was glad to be rid of him, hinting that they may have had a strained relationship. He has an aunt named Ottavio.
Lambo arrives in Namimori with the intention killing Reborn, however he is completely ignored and easily defeated by Reborn who lacks interest in him due to his refusal to associate himself with lower ranks of the mafia. After being defeated once, Lambo introduces himself to Nana Sawada, who assumes that Lambo is a friend of Reborn's and asks Tsuna to watch over them and keep peace. Tsuna takes Lambo to the riverside where Lambo talks about his goal to become the boss of the Bovino Famiglia and kill Reborn.
Lambo is later brought back to the Sawada household where he continues to try and kill Reborn by throwing a knife at him, however he fails after Reborn deflects the knife and sends it towards Lambo's forehead. While crying, Lambo brings out the Ten Year Bazooka, a weapon he borrowed from the Bovino Famiglia, replacing himself with his future counterpart from ten years in the future. Even as a teenager Reborn still continues to ignore Lambo, who uses his Electric Horns to seek revenge on Reborn, who interrupts him with a stab to the head with a fork. At the same time, he proves to be still a pathetic crybaby.
Lambo later reverts back to his present counterpart, with Nana disappointed that Tsuna didn't resolve one-sided argument (utterly oblivious to the true situation in the ouse).
For the most of this arc, Lambo tries to kill Reborn several times without much success. At the same time, he befriends Tsuna's mom and is soon a regular member of the Sawada household, much to Tsuna, Gokudera, and Reborn's annoyance.
During the Ring Conflict with the Varia, Lambo is chosen to be the holder of the Ring of Lightning, and he participates in the Lightning Ring Battle against Levi A Than. The night before the Lightning Ring Battle, Future Lambo appeared and told Tsuna about the Parallel Worlds. Future Lambo had no memories of the Ring Battles telling Tsuna that he could have been from a world where there wasn't a battle. He also requests Tsuna to tell that his past self not use the ten-year bazooka because 15-year-old Lambo didn't want to die fighting yet. The next night, during his battle with Levi A Than, he is shown to be able to use the Ten-Year Bazooka twice in a row, switching into his 25-year-old self. The 25-year-old self claimed that it had been a long time since he saw Tsuna and his guardians, indirectly revealing that Lambo's 25-year-old self is living in a world where Tsuna, Yamamoto, Reborn and Gokudera had supposedly been killed. He was unaffected by Levi A Than's most powerful attack and gains the upper hand in the battle. However, he turns back to his regular self due to the short time-limit of the Bazooka's effects. Just as he was about to be finished off, Tsuna saved him but ended up losing his Sky Ring along with Lambo's as a result. Lambo remains in critical condition afterward, but is forcibly made to participate in the Sky Ring Battle in which Levi A Than tried to finish him off before being stopped by Tsuna.
Along with the other Guardians, Lambo was brought to the future in the place of his future self. Kusakabe later brought Lambo, along with I-Pin and Chrome Dokuro, to the Merone Base. He later received a Vongola Box Weapon along with the other Guardians after the invasion of the Merone Base.
During the Arcobaleno Trials, Lambo is first seen being attracted by the glow of the Vongola Rings and asked Gokudera about them, who informed him all about the Arcobaleno Trials. Since then, Lambo was intent on finishing a trial. He then joined Tsuna during Fon's trial. At first, they couldn't catch him but when they used a plan, I-Pin sent Lambo flying into Fon, who landed in Tsuna's lap, ending the trial.
In Verde's trial, Lambo was angry when Verde popped his ball and asked him to pay for it. He then went running after Verde. On the beach, where Verde was, Lambo was sent flying and landed on Verde's ship. After most of the trial passed, Verde used an attack which paralyzed everyone; however, Lambo was not affected by Verde's attack due to his shock-absorbing horns and gets upset, starting throwing grenades around, ruining Verde's plan. Lal questions how Lambo is able to move and Reborn states that he is the Lightning Guardian, who is immune to electric shocks. Lambo then throws a grenade at Verde, stopping his attack. Colonnello flies over and picks up Lambo. Tsuna then attempts to finish Verde off with an X-Burner.
Gokudera was supposed to teach Lambo how to use his Weapon, but during training, Lambo, in a fit of rage, opened his Vongola Box Weapon by himself. The consequences of this weren't quite safe for Ryohei, who Gokudera was also supposed to train, and himself.
After returning to the past for the Inheritance Succession, Verde was supposed to be Lambo's tutor. However Verde was curious about Lambo's power to absorb shocks and analyzed him during his trial which took place at an amusement park. Lambo's objective was to reach Lampow (the first generation Lightning Guardian), who was hiding in the castle, and give him a paper stamped with three rides he had been on. Verde sent robots after Lambo in order to capture him. However, Lambo's extreme release of energy from Verde's previous experiments during the rides destroyed the machines. Despite not completing his original task Lampow noted that Lambo had fulfilled his role as the Lightning Guardian and gave him his inheritance.
Lambo later joined the others in order to save the girls from Daemon Spade and was separated from the others along with Ryohei. Lambo was then defeated by a doppelganger of himself but was saved by Hibari's rampage.
After the Choice battle, Lambo was tied up in his sleep and hidden under the sofa, allowing Torikabuto to impersonate him for the purpose of getting closer to Uni. But in the end, Uni and Chrome found out about Torikabuto's plan using their senses and I-pin found Lambo under the sofa thus leading Torikabuto and Tsuna into a battle . Later the group split up in the forest where the last battle would take place as Uni predicted and Lambo, along with Ryohei, Basil, Tazaru and Nosaru encounter Kikyo. Ryohei then uses the memory of Tsuna's mother ( Which Reborn assigned him to do when they are in extreme danger ) to get Lambo to release his Lightning Vongola Box. After destroying Velociraptor di Nuvola (Kikyo's box weapon), he falls asleep due to great loss of strength after opening his Vongola box and changing it to Cambia Formia. After Tsuna defeats Byakuran and everyone returns to the past, Future Lambo is shown along with the other Future Guardians waiting for Future Tsuna.
Before the Inheritance Ceremony, Lambo became good friends with Simon Famiglia member Large Ooyama. However, after the Simon betrayed the Vongola, he joined the others in invading Simon Island, although he was unaware of the grave situation. While Tsuna and Gokudera and Reborn were asleep, Lambo was lured down a hole by a rabbit, where he finds Large waiting. Lambo then tries to get Large to play with him, but Large claims that he is no longer Lambo's "slave." Large then says that once he has beaten Lambo he would kill the others. Lambo then declares that he would be the one to kill Reborn. Lambo then lights his Flame and upgrades his Vongola Gear Stone which Reborn states that it upgraded because Lambo would do whatever it takes to make Large play with him.
The stone then becomes the "Lightning Helm Version X." Large then says the rules of their fight will be sumo-style, with the first one to fall off the ring is the loser. As they start, Lambo complains that the Helm is too tight on him, which Gokudera says is because his hair is full of "useless crap." Lambo then takes the helm off as Large strikes him, and he is seemingly killed. As Large begins to gloat and lament that if Lambo were not Vongola and a few years older they could have been good friends. When Tsuna ask Lambo if he remembers the fight with Large, 15-year-old Lambo appears he says that he banged his head on the edge of the platform and that it knocked all of his memories of the past. After Large declares himself as the Mountain Guardian, Gokudera says to Lambo that he must put the helmet on and Lambo agrees. When Lambo put his helmet, he summons a new Gyuudon. Gokudera orders Lambo to go into Cambio Forma. Lambo doesn't understand that at first, but eventually goes into Cambio Forma and then Lampow's Shield appears in a new form, as a full suit of armor.
After overcoming some initial difficulties with the armor's weight, Lambo changes the form of the horns and the battle between Lambo and Large begins. In the first attack, Lambo is knocked over, due to Large's Mountain flame allowing him to synchronize with the earth. Lambo is discouraged to fight again, and when he is told the loser goes to Vindice Prison, he is less willing to fight. Eventually, Reborn and Tsuna voice their regrets of taking Lambo out of fear for his safety. Lambo then states that they are wrong, that in his memories, he was happy that he went with Tsuna and the rest of the Guardians, and that he always wished to grow up faster and truly be a part of Tsuna and the others. He says that Tsuna must always take him, and that he must win to be able to face his five-year-old self, and remembers how to use the Vongola Gear. He then charges his Flame, draws iron sand from the battlefield towards himself and forms the Elettrico Ironhorn, prepared to continue his fight against Large. He then charges Large with his "Ferro Corno Elettrico Shock," not only shattering Large's Ring Weapon and the flame-enhanced wall behind him, but also shoving him from the ring, making Lambo the winner.
After Large exclaims that the Simon's bond is strong because they all lost their families to the Vongola, the Vindice then appear and reveal the second key left behind by Vongola Primo. Large then asks Lambo if he thinks Tsuna has the makings of a great boss, to which Lambo replies no. He then explains that he's never seen Tsuna as his boss, but as a great brother and Large ponders if that could be a boss. As he is pulled away by the Vindice he exclaims that he will not forgive the Vongola, but accepts Lambo and with a smile says that he had fun with him. After Large is taken away to Vindice Prison, the 5-year-old Lambo returns eating corn. Lambo watches the fight between Tsuna and Enma when the fight is over he joke about Enma's hair and after that goes with the group to encounter Mukuro after he defeated Demon Spade. He gets trapped in an illusionary world with Gokudera like the others thanks to Demon Spade. However, he is freed with everyone else after Tsuna and Enma defeat Demon Spade. Later, he is seen at school riding on Large's shoulder after making him play with him all night.