Star appreciates Marco's help, advice, and kindness whenever she needs it, and she always finds ways to help him out when she sees she can. However, she has been shown to be resentful whenever Marco thinks she can not handle something on her own, and has on several occasions clashed with Marco over the differences between her adventurous personality and his cautious tendencies up to the point where she questions their friendship. Nonetheless, their friendship remains unbreakable, as demonstrated in "Gift of the Card" when they are prepared to die in each other's arms.
In "Sleepover", Star's feelings for Marco are implied to be something more than friendship, as when she yells out his name in frustration, the Truth or Punishment cube remarks "Truth. Star Butterfly has a crush on..." before being crushed.
In "Bon Bon the Birthday Clown", Star is initially happy for Marco when Jackie asks him to the school dance, but after seeing them together, she becomes dismayed. During her attempt at a séance with Janna, she tries to call Marco repeatedly and even resorts to using a dark magic spell to spy on him and Jackie. When Star sees Marco and Jackie together, her jealousy causes her spells to go out of control.Amethyst Arcade and lies about it to Star. Star forgives Pony Head after she saves Marco while being doomed to go to St. Olga's. In "St. Olga's Reform School for Wayward Princesses", Star shows that she cares enough for Pony Head to break her out of St. O's, the place she fears most, for her best friend's birthday. In "Pizza Thing" Star invites Pony Head to "Friendship Thursday", a regular event that she enjoys with Marco, and wanted Pony Head to be a part of too. Star Comes to Earth". Ludo is always trying to steal Star's wand away from her, and Star is always fighting with him and his army because of it. While disliking Ludo, Star does not see him as a huge threat that she can not defeat. She finds a lot of his plans ridiculous, and she does not appreciate it whenever Ludo and his army are making trouble or ruining things for her. Royal Pain" and "Camping Trip"), as well as a need to fight monsters.
Star has a harder time getting along with her mother. Not fond of her mother's strict rules and traditional sensibilities, Star liked being sent to Earth, which allowed her to get some space from her. At the same time, Star fully knows the danger of her mom finding out that she is being too reckless with the wand or exploring other dimensions without permission, which would lead her to be sent to St. Olga's. Regardless, the two love each other immensely. By season two, Star and Queen Butterfly's relationship is much stronger; Star is more comfortable approaching her mother with personal problems, such as in "Mr. Candle Cares", and Queen Butterfly is more appreciative of what makes her daughter special, as shown in "Game of Flags".
Tom is Star's ex-boyfriend. He still has feelings for her, but Star clearly does not feel the same way and she often pushes him away. However, she was willing to at least give him a chance to prove that he had changed and dealt with his anger issues. When it became clear that he had not, she responded by freezing him when he tried to attack Marco. In "Mr. Candle Cares", when Tom uses Mr. Candle to tell Star that all she is good for is being queen, he later realizes that he cannot win Star's affections, and apologized for trying to manipulate her. Although Star is on better terms with him after this, she still balks at the idea of spending time with him, as seen in "Friendenemies".Cheer Up, Star". She is highly impressed that he has "a record", and she fantasizes about being with him, much to Marco's annoyance when he is having a flashback.
In "Mewberty", Oskar is the focus of Star's new found attention on boys. After her transformation into a purple butterfly-like humanoid, she kidnaps both Oskar and his car and lifts him up to the sky. Unexpectedly, she then drops Oskar and his car back to earth, before returning to her normal state.
In "Star on Wheels", Oskar helps Marco save Star from a runaway bike ride. In the end, Star apologizes to Oskar about his broken car and offers him a ride home. In "Girls' Day Out", Star is unable to even speak with Oskar without becoming incoherently lovestruck.Monster Arm", they help wake her up so she could change Marco's mutated arm back to normal. In "Pixtopia", they accompany her and Marco to the pixie dimension, where she ends up having to save the two of them. Mewnipendance Day Reenactment, making her one of the "heroic" Mewmans battling against the "evil" monsters. In "Sleepover", Star invites her to her first slumber party. Laser puppy Star had conjured for her birthday gift; She pronounced the act "not cool". Mewnipendance Day re-enactment, and have her play a Mewman), but they develop a stronger bond in "Girls' Day Out" after Janna proclaims her "mayor of detention". The two have hung out together regularly since.