Alex is smart but not hardworking, much to the dismay of her older brother, Justin. Alex became a full wizard in Wizards of Waverly Place: The Movie, but later makes a wish through the Stone of Dreams to turn back time which, in turn, made her a student again (it would take a little while longer for her to achieve that title again).
In 2008, AOL named her the twentieth greatest witch in television history. Selena Gomez, who portrays Alex, is one of the only two cast members to appear in every single episode of the series to date; the only other cast member to appear in all episodes that have aired so far is David Henrie, who portrays Justin Russo. Alex has also appeared in The Suite Life on Deck and Hannah Montana.
At the end of the series, Justin came out of the tunnel first which meant he won but he made an explanation that Alex helped him get out of a vine. So, Alex became the family wizard. Since Professor Crumbs is going to retire, he asks Justin to be the Head Master which meant he got full powers. And Max becomes a mortal and is in charge of the sub station now.
But even with her full wizard powers, she still retains her sly, outgoing personality (in The Wizards Return: Alex vs. Alex). After an argument with her father, she decides to release all the negative emotions from inside her but this ends up creating a complete duplicate of an evil Alex Russo, who wants to take over the world.
Alex often argues and insults her brother, Justin. In the season three episode "Alex's Logo", while she is under a truth spell, it is revealed that the reason that Alex acts mean is simply because she wants to be liked and actually fears being hated.
Alex claims everyone takes her advice as she knows a lot about fashion, relationships, girls, and guys, but above all, she can be very sneaky and tricky to the extent that she's even willing to admit that she's usually up to no good, and feels uncomfortable when others say the opposite. Her best friend since childhood is Harper Finkle (Jennifer Stone), who often tries to keep her out of trouble, and is also her voice of wisdom. In the episode "Third Wheel", Alex says to Harper that she is like her sister. Her temporary best friend at Wizard School is Hugh Normous (Josh Sussman), as she said in one episode, that he was "the worst best friend ever". Though she continues to torment her older brother Justin, the two seem to have a close bond that neither seems to have with any other character on the show. Her enemy since kindergarten is Gigi Hollingsworth (Skyler Samuels), ever since Gigi spilled juice on Alex's blanket and told everybody that Alex had an "accident" during nap time.; however, as the series progresses, the rivalry quickly fades away. Alex often uses magic to solve her problems, which frequently ends up giving her even, more problems than she began with. Her tendency to use magic without permission is often caused by her lack of work ethic and respect for the rules she deems unnecessary. Alex hardly ever considers the consequences of magic and is often unprepared when the situation goes haywire, which requires the help of her more sensible brother Justin when she finds she cannot fix them by herself, often grudgingly accepting his offer to work together. Alex is shown to be at a lower level than Justin, but she is very skilled at "Make-'em-Ups" when a wizard can make up their own emergency spell. It is revealed in "Doll House" that Alex did not know about magic when she was five.
Riley (Brian Kubach) had been Alex's crush for most of the first season, and to impress him, she calls herself his good luck charm and manipulates Justin without him figuring out to magically win his — and Riley's, as she was always quick to emphasize — baseball game, though when Justin stops once their father makes him realize what Alex has been doing, Alex has to use magic herself by the bleachers in order to be Riley's date, cleverly managing to win the game for Riley even with Jerry and Justin's attempts to foil her magic, further showing how skilled she can be at magic by the way she countered Justin's magic so easily and discreetly at the baseball game where humans who did not know about magic were, despite Justin's and Jerry's knowledge of magic, when it clashes with her understanding of it — however, small her amount of understanding of it may be at the start. She had also got Riley jealous by enchanting a mannequin to come alive and date her—after he breaks up with her—in the episode "Alex's Spring Fling".
She is a Daddy's Girl and according to her father, Jerry (David DeLuise), she uses her puppy dog eyes to get out of trouble. She cannot tell when her dad is being overprotective, she just thinks he is being crazy and does not make the situation better by saying she is growing up. In "You Can't Always Get What You Carpet", however, she tells her dad she will always be his little girl. She is not fazed very much — if not at all — when he's overprotective and still does whatever it is he does not want her to do. For example, in "Alex's Brother Maximan", Jerry hears Alex tell her mom that her boyfriend, Dean (Daniel Samonas), wants to kiss her, and he says "Kissing? Who are you kissing?" and begins to freak out. Later in the episode, she does kiss Dean, but when her dad questions it, she tries to change the subject by saying something about him being proud of his children.
Alex is often depicted as a slacker, somewhat more so with regular high school than in wizardry and witchcraft school. If Alex does not want to do anything that is school-related, she will make an excuse or scheme about why she does not want to do it, and how unnecessary she finds it or will just simply not do it. She will often rebel against mandatory assignments with glee and has displayed little, if any, ambition, freely admitting that she always arrives in school during third period and never cares. She has been shown to be sent to the principal's office so often that she and Mr. Laritate have a regular routine down, even pouring each other coffee and giving each other donuts, and even has a pillow, a hammock, and a CD player containing rain forest sounds stashed in Mr. Laritate's office whenever she gets detention. She has even resorted to trying extreme measures in order to get out of a school project despite the cost being much greater, once going as far as deliberately attempting to injure herself by jumping off the stage after she is named as Harper's replacement as Tinker Bell in the school production of Peter Pan (this after she already auditioned to be Harper's understudy, thinking that she would not have to do anything in the play), when Harper accidentally falls off the stage during rehearsal. Art is her favorite school subject and is pretty much the only class she takes seriously and excels greatly at, being the best in her class and even being the co-art teacher.
After her parents complain how she never has never been in any school clubs, she lied and said she was in reading club and tried to steal the award from Justin's room and scratch out his name and put hers. Justin, however, is fed up with her always getting past his defenses to keep her out of his room and stealing his stuff, so he created Frankie ("Franken Girl") to guard his room, but Alex still managed to shut down Frankie when she figures out that Frankie's brain worked like a computer, and when Justin made Frankie immune to shutting down like a computer and cast a spell to make her think of Alex as her best friend — much to Alex's disdain — and Alex was then forced to put up with her before noticing that Frankie fit a lot of her best friend requirements, and became fast friends with Frankie. Justin then puts a spell on Frankie to like cheerleading and she wanted Alex to be on the squad with her. In "Monster Hunter", Alex gets jealous of Justin when he moves forward in wizard training so she creates a spell song where she can remember the spells she learns, hoping to catch up with him.
Alex and Justin act as foils, as the two are near-polar opposites in terms of personality; Justin is responsible, kind, selfless, sensible, hard-working, and fair in judgment, though not very witty with his words at times mostly like that just because he secretly competes to be the best at magic since he loves it but is easily insecure at witnessing Alex and her great magical feats accomplished so effortlessly by her. Alex is lazy, carefree, witty, funny, sarcastic, stubborn, and biased when it comes to herself or her loved ones against other people, magical or not, not very good at expressing herself in terms of emotions and frustration-causing desires on her part like wanting to be like Justin, cunning, mischievous, and a complete natural at magic despite not being as serious as Justin when discussed or performed, his performance full of constant measuring and intense concentration, while hers is laid-back and careless. Their similarities though are surprisingly many, despite how rarely they show themselves, as they are very strong during the moments they do shine through.
- The bad Alex has a streak of white hair, similar to the future Shego in Kim Possible: A Sitch in Time.
- She is like her Aunt Megan as they are both lazy.