As Hawk Moth, he is cold and determined. After a villain's defeat, he determinedly vows revenge and, while stopping for a while afterward, doesn't wait too long to try again with his akumas. His goal is to claim the Ladybug and Cat Miraculouses to gain their absolute power necessary to achieve his dearest secret wish, not caring if he causes people harm in the process. He is aware of the equivalent exchange drawback of making a wish with the Miraculouses, every wish having a reaction to maintain balance in the universe, but it doesn't appear to bother him.
He is also very stubborn as he refuses to listen to Nooroo about how he is using the Butterfly Miraculous, showing that he isn't remorseful about all the damage and chaos he is caused in Paris and also very desperate to save his wife.
Hawk Moth's akumatized villains are his most powerful known weapon, so he chooses his victims carefully, usually people who are emotionally at their weakest. He is a skilled liar and manipulator, persuading people that he cares about their problems and giving them powers to help solve them, when in reality, he does it because he wants them to retrieve the Miraculouses for him. He gives them ideas if they are struggling to think one up. However, if things aren't going his way, Hawk Moth easily loses his patience, threatening harm to Ladybug, Cat Noir, and even to the villains he creates. He also has a bit of a habit of celebrating too soon when the heroes get weaken by his many akumatized villains, thinking it will get him closer to the heroes' Miraculouses. He sometimes uses puns, such as telling the akuma in "The Evillustrator" to "draw Nathaniel into our evil web".
Despite these traits, Hawk Moth can be merciful with those he cares about, such as when he orders the supervillain to drop Ladybug in order to save Adrien who is falling off the building. He is obsessed with finding a way to save his wife, but is willing to give up his evil ways to protect Adrien from being caught in the crossfire or being targeted by the villains he creates. This situation, along with his frustration that even Audrey Bourgeois, who he believed was his greatest masterpiece, made him temporary renounce his role as a villain. However, he decided to continue to be Hawk Moth after Queen Bee appeared, viewing the opportunity to akumatize a Miraculous holder as too good to pass up.
Though his goal is specifically getting Ladybug and Cat Noir’s Miraculouses, when Gabriel tells Nooroo that he is going to kidnap the kwami friends of the latter so he can have unlimited powers at his disposal, it is implied that he has become power-hungry due to being Hawk Moth for a long time and has gotten addicted to yearning power to the extreme degree that he will grasp every opportunity to seize the power in order to have easier access on stealing the Ladybug Miraculous and Cat Miraculous.
That devastation has made his heart grow twisted by sadness, despair and desperation so much that he didn't care about the pain and suffering he caused to everyone else even his own son. In an alternate future of "Cat Blanc", it was those very feelings that led to his own demise.
- Hawk Moth's appearance is very different from his appearance in the Ladybug PV. In the PV, he doesn't wear a mask, has white hair and silver eyes, and wears a white dress suit with a pale tan vest and bow.
- The design of Hawk Moth's mask is a reference to the supervillain Fantômas from the 1964 French film with the same name.
- Hawk Moth is called "Butterfly" in other early sources.
- In the Castilian Spanish version, Hawk Moth's name is Lepidóptero, which comes from the scientific order called Lepidoptera, which contains all butterflies and moths.
- During Season 1 when his secret identity was unknown, there were clues suggesting that Gabriel was Hawk Moth are:
- Gabriel and Hawk Moth have the same voice actors in many dubs, including English, French, Castilian Spanish, Latin American Spanish, Italian, and Korean dubs.
- In "The Bubbler", it was not actually confirmed that Gabriel had been kidnapped by the bubbles of the titular villain.
- In "Mr. Pigeon", Gabriel was imaginated in Marinette's mind with a purple brooch resembling the Butterfly Miraculous.
- In "Ladybug & Cat Noir", the silhouette of the civilian form of Hawk Moth is very similar to that of Gabriel, and they seem to have the same clothes, in addition to having a picture of Emilie.
- In "Simon Says", Hawk Moth states that "it's risky" when he hears Simon Says say he will take Gabriel Agreste.
- In some dubs, Gabriel and Hawk Moth have different voice actors. Examples are the Brazilian Portuguese, Polish, Hungarian (only Season 1), and Dutch dubs.