Age: 13-15 pre-timeskip, 19-20 post-timeskip
Birthdate: December 13, 1989
Blood type: A
Likes: chocolate
Dislikes: those better than him

Mello is the older of L's two successors raised in Wammy's House, Watari's orphanage for gifted children, in Winchester, England, United Kingdom. When it is decided that Mello should work with the other successor, Near, Mello refuses, citing an inability to work with Near, to whom he is considered second. Similar to L's fondness for sweets, Mello is often seen eating bars of chocolate. How to Read 13 states that Mello has "an excellent mind" and that he "sometimes lets his emotions get in his way." The book cites Mello's "hatred of Near," which created "a flaw in [Mello's] personality." The book states that Mello isn't purely evil, citing his apology and genuine care for Matt's well-being. Tsugumi Ohba, the writer of Death Note, stated that Mello "works hard for everything." Ohba added that Mello's name "doesn't really stand for anything," as opposed to Near's name standing for Nate River, etc.

Mello is voiced by Nozomu Sasaki in the Japanese anime, David Hurtwitz in the English version and Javier Olguín in the Latin Spanish dub.