B'Elanna is half Klingon-half human. Her father is human and she hasn't seen him since she was five. Her mother is Klingon and is probably on the Klingon homeworld. They haven't kept in contact either. She grew up on a Federation colony on Kessik Four, where she often tried to hide the fact that she was half-Klingon. She now considers the Maquis to be her family, and is especially close to Chakotay. He has become her mentor, with his faith in her bringing out her good points. He thinks she is the best engineer he's ever known and could teach at the Academy.
B'Elanna can be quite angry and violent. Once she even broke Lt. Carey's nose over a minor disagreement. She is very competitive and excels in sports. At the Academy she was on the decathlon team. She enjoys Parisian squares and hoverball. B'Elanna even finished the hoverball championship with a broken ankle.
Her abilities as chief engineer are tested continuously as she must make due with the limited supplies of being the lone Starfleet vessel in the Delta Quadrant. She often comes up with revolutionary ideas that sometimes ignore Starfleet policies. In one of her finest moments as an engineer, she build an automated sentient being. However she was forced to destroy it.