Astrid is shown to be determined and extremely dedicated to becoming a Viking Warrior, and intensely patriotic of the Viking way. She is generally uninterested in the other teenagers, preferring to study and train on her own to become a better fighter. She is also rather short-tempered and always hits people who have angered her in some way. In the beginning, she has the most success in Dragon Training. She is shown to be serious and highly dedicated to one day fighting dragons. However, she was very kind and compassionate on many occasions and is shown to have a softer side, going out of her way to bring Snoggletog joy to Berk and she told Snotlout that it was harsh to call Fishlegs slow because of his weight. Regarded as the most proficient of the teenage Vikings, and possibly due to the pressure of this reputation as well as her innate pride, Astrid is initially shown as being something of a perfectionist, having incredibly high standards for herself, as well as a very low tolerance for competition, as she quickly becomes jealous. She later reveals a suspicious side to her as well. Astrid also has a caring side, although this is hidden by an initial attempt at violence to cover it up. Astrid is one of the most knowledgeable in dragons, knowing of various breeds' shot-limits, behaviors, and of course she specializes in Deadly Nadders, like her dragon, Stormfly. When it comes to her dragon, Hiccup and Toothless, Astrid is somewhat kinder and gentler. She cares deeply for them, and has come to love Stormfly, who in turn is loyal to her, being there to greet her in the morning when Astrid wakes up. The bond between Astrid and Stormfly appears to be very strong, especially when Stormfly allows Astrid to touch her babies. She often provides her form of advice called the Honey and the Hatchet (you tell someone what they want to hear, the honey part, before you hit 'em in the head with something they don't, the hatchet part). She also seems to have a great deal of knowledge of the 'Viking traditions'. Due to her pride and rather short temper, she could sometimes be somewhat imprudent and could act before thinking things through. At these times she would put herself in grave danger despite the fact that the odds were very clearly against her.

Astrid has grown more mature, as she doesn't seem to be as serious as before and seems to enjoy hanging out with her fellow teen Vikings more. She also seems to have gained a better sense of humor.