Deidara had slanted blue eyes and very long blond hair which he wore drawn into a half ponytail with the rest hanging down freely. The bang hanging over his left eye is what concealed his eye scope signifying that he was a long-range fighter, but as shown in his fight with Sasuke, it was not permanently attached to his face. He also had mouths in each of the palms of his hands which were used for molding his clay and under his cloak he wore a utility belt with two bags where he carried all of his clay. Deidara had one of his arms crushed by Gaara's sand, and the elbow of his other arm was blown into another dimension by Kakashi's Kamui. Deidara had his arms restored by having Kakuzu sew what was left of his arms with what appears to be a transplanted arm. His transplant was dark brown and had several wrinkles on it. Under his standard Akatsuki black cloak with red cloud patterns, he wore a V-neck, sleeveless, midriff shirt with mesh armor underneath it along with pants, stirrups, and sandals.
On the left side his chest he had a large, stitched-up mouth for setting off his self-destruct technique. On his right index finger was his Akatsuki ring, which bore the kanji for "blue or green" and was teal in color. He wore black nail polish on his fingers and toes.
During his partnership with Sasori, Deidara usually showed a cool, and relaxed attitude, never losing his smirk even while fighting an intense battle or when being blamed by his partner. However, his personality seemed to change to some extent after being partnered with Tobi, as he would easily get mad at his partner’s childish and sometimes disrespectful behavior. He also had something of a sadistic arsonist nature, rather he was not above enjoying a good fight, and he often blew up his opponents in a very brutal fashion. Deidara's most distinctive trait, however, was his love of art. He would respect any form of it, even if it disagreed with his own. Deidara also had a habit of ending his sentences with nasal-like grunts, roughly translated as "yeah" or "hm". Deidara also seemed to respect the ideals of others as he allowed Gaara to move the sand he used to protect his village into the desert before kidnapping him, even going so far as to admiringly call him noble.
Deidara referred to his explosive ninjutsu as art, usually quoting "Art is an Explosion!" and seeing each bomb he made to be a significant accomplishment. He referred to his style as super-flat (referring to certain types of art), and claimed pop (another art style) is dead. He would often boast about his works of art, even towards his opponents in battle. Deidara's pride as an artist makes him simply unwilling to accept that anything could defeat it, leading to his abandonment of strategy during his battle with Sasuke Uchiha, in favor of tactics that let him show off his art. He was able to recognize stronger opponents like Itachi, although he felt that the Sharingan was inartistic, and despised the fact that he had been enthralled by its genjutsu.
Deidara referred to his partner Sasori as Sasori, my man, out of respect for him as a fellow artist. He also admitted, at least outwardly, that Sasori was more powerful than he was. In spite of this, Deidara wasn't above goading his partner, and they frequently argued over the nature of true art (Deidara holding that art is what lasts within a moment while Sasori believing fine art is something that lasts for all time). This reflected their individual fighting styles (Deidara made clay sculptures that exploded; Sasori made long-lasting puppets out of humans). Deidara outwardly seemed to respect Sasori's beliefs, but couldn't resist getting a final jab in after Sasori's death.
Explosive Style Kekkei Genkai: Deidara possessed the Explosive Style kekkei genkai. This allowed him — by simultaneously using earth and lightning chakra natures — to give his chakra explosive qualities. Deidara also possessed special mouths in the palms of his hands and on the left side of his chest as a result of stealing and using a powerful kinjutsu from his village on himself. By commonly using these two special abilities in unison, he could create explosive clay: clay infused with his explosive chakra that detonated with the command Katsu and the seal of confrontation. This clay could be molded into a wide variety of shapes and forms, growing to large sizes when infused with chakra (with Deidara performing the necessary hand seals), and could be controlled at will. This allowed him to create living explosives to attack opponents at long-range. Deidara could even create clones from the clay and named Suicide Bombing Clones, that could be a deadly surprise for opponents and if need be create clay minions to control with a cord from a distance. Deidara's clay creations ranged from microscopic to gigantic in size, allowing him to adapt to any situation from creating dragons to shoot smaller clay bombs, to working in conjunction with Obito to lay explosive clay landmines under ground to limit the opponent's movements. As an ultimate last resort, Deidara could turn himself into a bomb by devouring explosive clay that has a large blast radius in which he calls his "Ultimate Art". Deidara could also use the clay for other purposes, as he was frequently seen creating birds to be used for transportation which also function as a way to easily infiltrate villages on missions. It seemed he also knew standard earth-based techniques, as shown from his Earth Style: Hidden Mole Jutsu, which he used to avoid damage from one of his mass-scale bombs. However, he could potentially run out of clay if he used too much of it, leaving him vulnerable. Since all of his explosives were earth-based, they were vulnerable to lightning, and most could thereby be defused with lightning-based attacks.
Expert Hand-to-Hand Combatant: As a long-range specialist, Deidara was weaker in close combat, but he was skilled enough to fend off a close combat battle against specialists like Team Guy, despite having lost both of his arms prior to their confrontation (albeit he was completely on the defensive), using only a kunai in his mouth and a variety of techniques in his arsenal to escape close-quarters when necessary.
Enhanced Speed and Reflexes: His stealth skills are rather proficient as he was able to sneak up on a few Hidden Leaf Anbu and plant clay bombs on them unnoticed. He could also avoid a blitz by Sasuke, though he noted the Uchiha's speed was too fast.
Enhanced Endurance: Deidara also had great endurance to pain, being able to keep focused after having both his arms torn off.
Enhanced Strength: Deidara also had great physical strength, able to pull himself free from Gaara's chakra-infused sand and sever what was left of his arm at the same time. He could also dislodge two giant shuriken from his arms using his feet.
Keen Intellect: One of Deidara's strong points was his intelligence, often using tricks, misdirection, and calculated gambles to get his explosives in range of an opponent. He demonstrated these skills in his fight with Gaara, putting clay into Gaara's sand as it destroyed his arm. During his battle against Sasuke, he managed to trick him on a few occasions, such as trapping him between his C2 dragon in the sky and the landmines buried underneath the ground by Tobi, and again when he lured him into his C4 attack at point-blank. In the Naruto anime, Deidara managed to deduce a workaround to his weakness to Lightning Style by using a sword as a makeshift ground rod to siphon off the lightning-based attacks his explosive clay was weak against.
Eye Enhancement: Deidara wore a scope on his left eye for long-range observation, and he had trained the eye itself to counter genjutsu, allowing him to see through and negate them. When he did this, his pupil would contract. This training was done in order to counter Itachi's powerful genjutsu skills, of which he had a considerable loathing, and wished to defeat if he got the chance. Deidara seems to be able to see long distances without his scope as after being reincarnated, he found enemy shinobi lurking near Tobi's hideout; he still needed to close his right eye in order to use his left eye for long distance vision.