Spike is a bounty hunter who was born on Mars. He is 27 years-old; an indirect reference to the 27 Club. In appearance, Spike is tall and thin, but with muscular shoulders. He is attractive, with fluffy dark green hair and reddish-brown eyes, one of which is artificial and lighter than the other. A flashback in Session 6 revealed it was his fully functioning right eye which was surgically replaced by the cybernetic one (although Spike himself may not have conscious recollection of the procedure since he claims to have lost his natural eye in an "accident"). He is usually dressed in a blue leisure suit, with a yellow shirt inspired boots. Spike often has a cigarette between his lips that's rarely in good condition, sometimes despite rain or "No Smoking" signs.

Spike has many talents and abilities, making him an excellent bounty hunter. He has very sharp eyesight and abnormally acute perception, and is extraordinarily lucky. Spike makes use of sleight-of-hand techniques to win card games, pick pockets, and even to slip things onto other people unnoticed. Where Spike really excels, however, is in combat. He is well versed in weaponry (such as his personal Jericho 941 as well as other guns and explosives) and hand-to-hand combat skills. He follows Jeet Kune Do, the mindset developed by Bruce Lee, though he has a penchant for high kicks of French boxing. Spike is also an excellent pilot, and flies a converted Asteroid racer called Swordfish II which is armed with four machine guns, multiple missile launchers, and a single plasma cannon.

When he's not working or practicing martial arts, Spike is very laid back and lackadaisical, often a source of consternation for his crew mates. Some members of the Bebop crew occasionally refer to him as a "lunkhead" due to his attitude, and generally Spike just takes life as it comes. He also enjoys sleeping and that may tie into his mantra of 'living a dream.'

Spike's philosophy seems to be based on the ancient samurai ideals of immediacy: considering oneself as dead and the idea of death being an awakening from a dream are both elements of bushido illustrated in the Hagakure.

Watanabe has admitted that Spike has a habit of being very indirect with his emotions, for example behaving antagonistically towards someone he actually likes. He says that this could apply to Spike's relationship with Faye.

Another possible hint at Spike's preference of Faye are the similarities between Julia and Faye, many of which are recounted here. One of which is a scene from the end credits of the show (Spike's flashback), which shows Julia wearing an outfit remarkably similar to Faye's.

Spike is also heard saying that the three things he hates most are kids, animals, and women with attitudes. He asks Jet why all three are on board

Some years prior to Session 1, Spike had been a rising member of the Red Dragon crime syndicate where he was partnered as a sweeper and enforcer along with his then best friend, Vicious. Badly injured after a shoot-out in the slums on Mars, Spike stumbled to the home of Julia, Vicious' then girlfriend. The pair fell in love while she nursed him back to health. Spike decided to leave the syndicate and elope with Julia. Realizing that his best friend had essentially gone soft and fallen for his girlfriend, Vicious gave Julia a painful ultimatum: to either murder Spike or Spike and Julia would both face death for her betrayal. Although the specifics of the incident are unclear, Spike apparently managed to fake his own death by engaging in a gunfight alone in a church against a rival syndicate; this allowed him to drop off of the Red Dragons' radar. He waited for Julia so they could escape and be free, but she never showed.

One of the recurring themes surrounding Spike's character is how he views himself and his life. He claims that one eye - his right one, the prosthetic - can only see the present, and the other - the left, his real eye - can only see the past. This is revisited by a close-up on Spike's left eye every time he has a flashback of his life before coming aboard the Bebop. He seems to regard his false death as real in some way, saying that after that day, he had "merely been living a dream". (Interestingly, during Session 25 when Spike has a flashback of the last time he saw Julia, the close-up shows both Spike's eyes, perhaps implying that his future and past are now the same.

Spike's attitude of living in a "dream-like" existence is displayed by his careless behavior and his nonchalant attitude towards dangerous or outright fatal situations. One quote that exemplifies this is in Episode 1.

Some time after his "death", Spike met the former ISSP cop turned bounty hunter Jet Black, and the two men became partners. Spike moved onto Jet's ship, the eponymous Bebop and the two men worked together for about three years before being joined by the other crew members.

Spike is generally thought to have died of wounds sustained in his final duel with Vicious, and the fading star in the ending theme of the finale is thought to support this claim. In an interview, Watanabe stated "I've never officially said that he died. At this point, I can tell you that I'm not sure if he's alive or dead."He also stated that he believes fans would be upset if there was a continuation. The later Cowboy Bebop movie Knockin' on Heaven's Door was set before the end of the series.