Age 25 in Shippuuden.
His parents died during the attack of the nine tailed demon fox (Kyuubi) at the village. Since he was a child he had a sort of sorrow and sadness, but pride as well, because he knew his parents had an honorable death as other brave shinobi did, protecting their home. Due to that past and unfortunate event, Iruka has always had very significant support from the Third Hokage, they were relatively close with eachother. Much later as the Third Hokage's funeral was occurring, he remembered how the Third had comforted him when he was crying at the memorial stone of the village's heroes who had died while on duty. It was there that the Third told him about the “Will of Fire”, the will to protect each and everyone of the village of Konoha and see everyone as a family, and Iruka affirms that he bears it as well.
Iruka graduated from the Leaf ninja academy at age 11, and became a chuunin at 16. He then later he became a teacher at the same ninja academy where he had previously studied, always having the “will of fire” as a substance of his teaching. It was there while teaching at the academy that he would meet and teach Naruto, and all of the other rookie students who were studying to become ninjas. Even though a gentle and dedicated teacher if necessary, Iruka can also be very strict with his students and often lose his patience and yell at them when they show a certain laziness or indifference toward the class subjects, or simply do not put in enough effort.
As one of the first characters to be introduced, we become aware of his connection with Naruto, since Naruto was a troublemaker it the beginning of the story we see Iruka lecturing him to be more serious, and also used to tell him to stop inventing worthless techniques such us the “Sexy jutsu”. He also had failed Naruto at the exam since he could not create a proper clone (bunshin no jutsu). Another chuunin teacher named Mizuki took that chance to deceive Naruto in order to acquire a forbidden scroll of seals which was in Sandaime Hokage’s possession, it’s there were we see Iruka protecting Naruto from Mizuki and expressing how he sees Naruto as a brother and also similar to him since he had the same sort of childhood, no parents, to like to make some pranks in order to draw attention, and they both share the same likeness about ramen, the delicious food he always took Naruto to eat at the Ichiraku’s place. Naruto also protects Iruka by making a large amount of shadow clones a technique he learned from the scroll he took (further details about that event can be consulted at Naruto’s biography).
Continuing, it’s there that after defeating Mizuki with the innumerous shadow clones, as the sun was rising, Iruka tells Naruto to close his eyes and then to open, and says “Congratulation on graduating” and Naruto notices Iruka has put is own leaf head protector on his head, and that is one of the most important moments of Naruto the moment he became a ninja.
As Naruto had a new teacher, Kakashi, Iruka kept always watching and worrying about Naruto even though he is no longer his teacher always wishing good luck for him in his journey to become Hokage, he also worried about Sasuke and Sakura, we can confirm that right before the chuunin exam took place Iruka disagreed with Kakashi that they (Naruto, Sakura, Sasuke and the other new genins) were not ready to face that exam, and had a sort of discussion with Kakashi, because of a preliminary test was taken in order to know whether they were ready or not, Iruka himself disguised as a ninja from the Hidden Rain village (using the Henge no jutsu or Transformation technique) test all the 9 rookies and later he tells Kakashi they all passed. We also see Iruka taking care of the children during the Konoha invasion, he led them to a safe place located in the mountain with the Hokages sculptures, a few days after he comforted Konohamaru while he was crying because his grandfather which was the Third Hokage Sarutobi had perished, Iruka explained Naruto about the life of a Ninja and why they sacrifice their lives to protect those they care.
As the Fifth Hokage was chosen, Iruka although inclined for teaching went for missions and almost all other ninjas as well so that Konoha could remain considered as a reliable and powerful village as it has always been.
At the Shippuuden Iruka has for appeared a few times, after Naruto returned from his training with Jiraiya and after Kakashi had tested his growth Iruka joined Naruto at the Ichiraku’s ramen place, they talk about Naruto’s training, how Gaara was Kazekage already, Naruto even tells he could have surpassed Iruka already. Iruka keeps teaching at the academy and also participates at the missions delivery supporting the Hokage (actually is Tsunade one of the three legendary ninjas). One exquisite and unique characteristic we can find about him is a sort of horizontal mark or scar he has a few inches above his nose.