Din Djarin was a strict follower of The Way of the Mandalore, a set of ancient traditions passed down from the Children of the Watch, the orthodox Mandalorian sect that rescued him as a foundling and brought him into their fold. Dedicating his life to their teachings, he was unaware of any other way to live as a Mandalorian until he encountered Bo-Katan Kryze and her fellow Mandalorian warriors, who explained what being a Mandalorian truly meant.
While her revelations made Djarin question his upbringing, in truth he had been straying from the Mandalorian Code of Honor ever since encountering Grogu. The laws and ideals that governed his warrior culture began to slip away in subtle ways and not so subtle ways as they bonded throughout the series until, finally, he was able to remove his helmet in front of others in order to rescue him.
When Grogu Helped Him With The Mudhorn
One of the tenets of the Mandalorian Code explains that "with no honor one may as well be dead", which was illustrated early in Season 1 when Din Djarin acknowledged that the death of the Mudhorn attacking him wasn't honorable because Grogu helped him.
The Mandalorian felt he should have been the one to kill the beast, and he knew the confrontation afforded great risk, and he might be the one to die in battle. This would have been acceptable and in accordance with The Way, but with the tiny Force user's help, one aspect of the Code was not observed.
Taking Imperial Beskar
After performing his job for The Client and successfully placing Grogu in Imperial hands, Djarin was paid handsomely for his efforts; a camtono of beskar. He used it to not only get new armor forged by the Armorer, but to provide the foundlings of the Tribe with the excess for their needs.
While his actions appeared generous, several members of the covert took umbrage with the fact that he received the beskar from the Empire. It seemed to break with the Code of Honor, and Paz Vizsla called him a coward while engaging him in battle with a vibroknife.
When He Forced His Cohort To Find A New HQ
After Din Djarin broke the Bounty Guild Code to retrieve Grogu, The Client's operatives came to take their asset back for more experimenting, which resulted in a firefight that pinned him and his ward down. A group of Mandalorians appeared to provide cover, allowing him just enough time to escape with Grogu Off World.
Mando informed the Heavy Infantry Mandalorian that the group would need to find a new space, as only one Mandalorian was ever permitted to be seen at a time to hide their numbers. Had the Mandalorian not chosen to concern himself with Grogu's fate, he would not have been seen with more than one of his kind and placed them all in potential danger.
When He Removed His Helmet To IG-11
Keeping his helmet on was crucial for Din Djarin, not only to protect his identity but to preserve The Way according to the Children of the Watch. If he removed his helmet, he would never be able to put it back on. He did so in the Season 1 finale because the extent of his injuries required IG-11 to have access to his face.
Though IG-11 wasn't alive, exposing himself to the droid still broke the Code of Honor in Mando's eyes, but he was willing to suffer the consequences because of his devotion to protecting Grogu.
When He Doubted Bo-Katan's Right To Rule
As it turned out, Din Djarin was ignorant about the ways of his people. When he encountered Bo-Katan Kryze in Season 2, from an old and established aristocratic house on Mandalore, he doubted her legitimacy to rule and even the existence of the darksaber.
One of the tenets of the code is "the strong have the right to rule", and because she chastised his adherence to The Way followed by the Children of the Watch, he didn't take what she said seriously when she had every right to assert her claims and her heritage.
When He Resisted Bo-Katan's Call To Action
There is an important part of the Mandalorian Resol'nare, or Six Actions, which make up the Mandalorian Code from Star Wars Legends, and from which the Mandalorian Code of Honor is transcribed; answering the Mandalorian leader's call to action.
By all accounts, Lady Bo-Katan Kryze should be the rightful ruler of Mandalore, and when she directs him to seize an Imperial cruiser for her war effort, he initially refuses. Din Djarin isn't very trusting by nature and doesn't put a lot of faith in the societal workings of Mandalore, but he should have honored her request because she asked it, not because it would help get Grogu back.
When He Doubted Boba Fett's Claim To His Armor
There's only one other Mandalorian more famous in the Star Wars franchise than Din Djarin, and that's Boba Fett who, despite not being a true Mandalorian by blood, still comes from a line of respected foundlings. His father, Jango Fett, once fought against the Death Watch to protect Mandalore.
One of the tenets of the Mandalorian Code is devoting one's self to the welfare of the clan, and honoring other Mandalorians and their sacrifices. By doubting Boba Fett's right to his father's armor, Djarin rebukes the tenet and discredits Fett's clan as warriors who fought to preserve the Mandalorian way of life.
When He Didn't Use Mandalorian To Prove Heritage
Another specific component of the Resol'nare is speaking the Mandalorian language, which Din Djarin doesn't seem to do even among his own kind. It seems like a perfect way to determine whether or not Cobb Vanth, Bo-Katan, Boba Fett, or any of the other Mandalorians he meets are in fact Mandalorians or those pretending to be.
In the series, he's seen conversing with a variety of galactic citizens, from signing with Tusken Raiders to attempting to speak Jawaese (his Jawa "sounds like Wookiee"). He appears to make an attempt at a variety of tongues but his own.
When He Tried To Give Grogu To Ahsoka
When the Armorer put the Mudhorn signet on Din Djarin's armor, she did so to symbolize the bond between him and Grogu, not the strength he showed in combat. She declared that they were a Mandalorian "clan of two", created out of their unique circumstance, and one that could not be abandoned regardless of its formation.
Yet that's what Djarin did when he presented Grogu to Ahsoka Tano. While the Armorer did tell him that he needed to take Grogu to his people, she did not specify that they be parted. By the time Luke Skywalker arrived to collect Grogu, Mando seemed to have taken their bond more to heart, and wasn't willing to give him over to the Jedi Master at first.
When He Removed His Helmet To Assist Mayfeld
When Mando and Migs Mayfeld successfully infiltrated the Morak Imperial refinery, they were nearly able to complete their mission save for one catch; Mayfeld possibly being detected as a deserter. In order to access the secret files pertaining to Moff Gideon's ship, Mando had to remove his helmet to allow the Imperial facial scanner to map his face.
It was the second time he'd removed his helmet in front of someone else, but the only time he'd done so while in the company of organic lifeforms (IG-11 didn't count). The action was a testament to how much he was willing to sacrifice to save Grogu, and to his credit, Mayfeld didn't interact with him any differently.