Donatello is quieter and more reserved  than his brothers. He does not have Mikey's outgoing nature or ability to make friends quickly, but his loyalty to the friends he does make is considerable. He also has a tendency to take things personally and deeply to heart, such as the care and protection for The Pulverizer and being the most upset by April's departure after the mutation of her father. Donatello is a bit awkward in social situations; having neither Leo's charisma or Raph's indifference to what people think.

Donnie isn't not without faults. He is nervous, easily annoyed and, while not prone to regular bursts of anger like Raph, he can lose his temper, especially when technology fails or performs ineffectively. He is also rather romantic and very loving. He is able to appreciate the love between his father Splinter and his late wife, as well as the growing affection between April and Casey. 

Donnie is particularly skilled, having "a way with machines" and is the most intellectually inclined of the siblings. Of all of the turtles, he has devoted more of his time to non-combat oriented pursuits, such as the study of technology, biology, chemistry, mathmatics, and metallurgy. This makes him very nerdy, especially in the eyes of Raph. Donnie is the 2nd most mature out of all his brothers, aside from Leo, and often is the voice of reason and logic. In previous incarnations, Donnie is seen as second-in-command, but no such title has been established in this series, thus far. 

Donnie is a skilled martial artist but often puts more faith in his gadgets and machinery than the more traditional methods taught to him by Master Splinter. Donnie tends to clash with Leo over these "traditional methods", as seen with Metalhead and later, the Turtle Mech.