The nicer and compassionate Winchester on Supernatural has always been Sam, who didn’t have the level of explosive emotions as his brother Dean. However, it’s Dean who’s had more friendships than Sam, owing to his more outgoing nature and forming connections to others in his adventures.
But that doesn’t mean Sam didn’t have genuine friendships of his own, with more than several names being noteworthy. As Bobby was his surrogate father and Jack his surrogate son, these relationships don’t qualify as friendships since they were familial. Likewise, love interests fall in the romance category, leaving the characters with whom Sam had a friendship based on trust, chemistry, and lasting impact.
Crowley
For a few years, Sam and Crowley had a much better relationship than the latter had with Dean, as Crowley had even confessed his need to be loved to Sam in a moment of vulnerability. They continued to help each other out in later seasons, although this was weakened due to a number of factors.
This mostly had to do with Sam attempting to take Crowley’s life when Rowena tasked him to do so in return for a favor. Following this, while Crowley somehow overlooked what Sam did, their “friendship” was based around mutual assistance rather than Crowley feeling a connection to him as he did with Dean.
Gabriel
In his own way, Gabriel actually really cared about Sam, with the latter’s influence allowing him to grow as a character. Gabriel connected to Sam also being the youngest sibling, along with the burden of responsibility that fell on him.
Gabriel trapped Sam in his time loop to make him see that he needed to move on from Dean, even allowing Dean to be resurrected purely because Sam asked him. Sam also didn’t blame Gabriel the way Dean did for abandoning Heaven, as he understood what it was like to feel trapped among family.
Amy Pond
This is a relationship Sam should have stuck with, as Amy ended up taking other people’s lives when her monster tendencies got out of control. Amy didn’t officially become Sam’s romance, as things never took off once Amy had to kill her mother to save him.
They reconnected their friendship in the future when Sam covered up for Amy after she had to kill people to feed her son. The reason why this friendship is so notable is the fact that Sam cut himself off from Dean after finding out the latter had killed Amy, meaning he valued their friendship so much that he became estranged from his own brother.
Kevin Tran
Due to all the times the Winchesters didn’t help Kevin when he needed, there are enough reasons not to consider them friends. However, Sam and Kevin always had a close relationship whenever they were on the same page, with Sam being the one to be compassionate to Kevin’s plight as a prophet.
Dean tended to ask too much of Kevin, while Sam was the one to be easy on him and listen to his issues. Kevin had also considered Sam to be a better friend than Dean, although Sam choosing not to look for Kevin after Crowley captured him certainly would’ve been on Kevin’s mind.
Sully
For a very long time, Sam considered Sully to have been a figment of his imagination, not realizing he was a Zanna who made it his job to provide the 9-year-old Sam the comfort of a friend. After thinking Sully wasn’t real, Sam ordered him to leave so he could grow up.
Decades later, Sully returned to Sam’s life where the latter apologized for his behavior earlier. Sully showed he still knew how Sam felt inside, as the two reconnected instantly, this time with Sam appreciating all the help Sully provided to him as a child.
Charlie Bradbury
Fans generally wanted the original Charlie to return for Season 15, as the alternate version didn’t have much of an impact. Regardless of which Charlie it was, though, Sam always managed to get her to be her true self and not use the history of the alias she had.
Charlie became a sister figure to Sam, as he shared his problems with her to which she provided answers. He trusted her in his plans to find a way to cure Dean of the Mark of Cain, which she did to the point of losing her life.
Garth Fitzgerald IV
Unlike Dean, who found Garth to be annoying, Sam was always willing to indulge in his show of affection. Sam also considered Garth a valuable ally without ever making him feel as if he were any less. His compassion toward Garth was such that he didn’t care when Garth turned into a werewolf.
Garth appreciated Sam’s friendship so much that he named one of his children after him in tribute — Dean didn't get this honor. It was clear that Garth felt safe being around Sam, seeing as Sam liked Garth for who he was and was sympathetic to his problems.
Jody Mills
Jody was one of the few who treated Sam and Dean the exact same, being a combination of a mother figure and an older sister. In turn, Sam was there to comfort her after the loss of her husband and resurrected son.
Their friendship was so strong that Sam could show up unannounced and expect to be treated like family, with Jody’s cooking the only “home food” the boys had. Jody also ended up becoming a full-on hunter thanks to the training provided by Sam alongside Dean.
Rowena MacLeod
Due to starting out as an antagonist, there were some ways Rowena got worse. However, she became much better where it mattered the most, all thanks to her growing relationship with Sam. By the end of Rowena’s life, Sam had easily become her closest friend.
After initially forcing her to help, Rowena softened her disposition to become an ally and bonded with Sam so many times that he also became trained in witchcraft. Her fated demise at his hands broke Sam’s spirit, as he acknowledged Rowena’s assertion that they really had become very fond of each other.
Castiel
Their relationship was always so sweet that fans have taken to dubbing them as “Sasstiel.” With the revelation that Castiel was in love with Dean, it means he considered Sam to be his actual best friend. In fact, their relationship was far better than Castiel and Dean's since Sam never created conflict with Castiel.
Sam also didn’t have any other friends that came close to the level of trust and constant contact he had with Castiel, and he instantly forgave him for his part in Mary’s death. Where Dean cut off his friendship with Castiel in Season 15, Sam actively tried to get him back. Of course, Castiel valued Sam so much that he straight-up entered Lucifer’s cage to retrieve Sam’s soul.