Professor Justin Vincenzo Pepé Russo (portrayed by David Henrie) is the eldest of the Russo kids and is a full wizard like his younger sister Alex. He's one of the most gifted wizarding students of recent times, creating his own spell, being able to use the Russo family wand with amazing success, and being well viewed by adults and professors, both mortal and magical. In the show's finale, Justin keeps his wizard powers, replacing Professor Crumbs as the new Headmaster of Wiz Tech.
Even though Justin has had many romantic relationships through the run of the show, his most significant relationship is the relationship with Juliet van Heusen, which is ongoing.
Justin is one of the most intelligent and posses vast knowledge, both of magical things, such as spellcraft and magical creatures, but also mathematics, history, robotic and geography. He's capable of built robots, water motors and mechanisms that simulate a flying carpet. His own knowledge makes him the chosen by his family to solve problems, like found excuses to hide magical affairs to protect magic from exposure.
Justin is labeled by his own family to be kind and generous but also has a vengeful and naive side. He strongly believes in aliens and that the language spoken by the Alien Language Club is actual alien and not make 'em up. He's shown to be gullible as seen in Wizards Exposed, when Justin was interrogated by the government, he was manipulated into telling the truth about being a wizard by claiming to him that they found an alien transmission from actual aliens, but due to his obsession for aliens, he actually believed that the transmission was from actual aliens and in Who Will Be The Family Wizard when Justin actually thought he was disqualified from the Wizard competition and kept resenting Alex, but actually turned out to be another one of Crumbs' hidden tests to prove if they can live well without magic, and can sometimes self-centered, as proven when he found out that Alex was back in the competition and won a Wizard of the Year award and expressed his envy towards Alex's win, including when he and the family traveled back in time in the 50's with Harper and left her behind with Justin refusing to go back and get her back and refused to not rescue his best friend, Zeke, from a griffin to focus on the competition and likes to be the center of attention, being sometimes deceived when he's praised.