Raised on an unnamed planet with pollution so thick the stars were not visible, Wash became a pilot in part to see the sky beyond his home. According to the Serenity novelization (which is not considered canon), Wash was second in his class. Mr. Universe, Wash's friend in flight school, was top of the class, since he hacked the records. In order to buy Wash's silence (and save himself from a threat of bodily injury at the hands of Wash), Mr. Universe offered Wash his services whenever they were needed.

Wash served in the Unification War. On the commentary on War Stories, Tudyk says that Wash served as a pilot during the Unification War (he did not specify which side, but it is probably safe to assume he was either a Browncoat or freelancer, since it is highly doubtful Mal would hire an Alliance pilot, regardless of his skill and recommendations). However, his ship was shot down and he was put in a POW Camp where he spent the remainder of the war entertaining the other prisoners with shadow puppets.

Wash then travelled widely, visiting odd worlds where, for example, juggling goslings is the principle form of entertainment. His skills as a pilot grew, and by the time Wash met Malcolm Reynolds, his reputation had grown to the point where he was actively courted by multiple captains in search of a good pilot. Wash accepted Mal's offer, and in the course of time, fell in love and eventually married Reynolds' second-in-command, Zoë. This pairing is especially ironic, given that Zoë's first impression of Wash was one of immediate dislike and distrust. The two have a passionate and strong relationship, despite Wash's occasional concern over Zoë's strong personality and her tendency to assume the more aggressive, traditionally male role in the marriage, a concern that is compounded by Zoë's fierce loyalty and devotion to another man — her commanding officer, Mal.

A laid-back guy with a dry and occasionally whimsical sense of humour, Wash tends to represent the pragmatic, cut-and-run opinion in any shipboard debate, and often serves as the calming influence in heated arguments. His actions sometimes appear cowardly (or at least less than heroic), but Wash has proven his resolve and willingness to both put himself in harm's way and do violence on behalf of his friends on many occasions. His loyalty to his fellow crew is unshakeable, as was shown when he insisted on rescuing Mal from the clutches of the crime lord Adelei Niska, despite having been severely tortured by Niska himself to the point of barely being able to stand.

As a pilot, Wash's flying style oscillates between near panic and a Zen-like calm. The attitude he conveys seems to be in inverse proportion to the degree of danger he believes he and the ship are in at any particular moment, acting the most calm when facing the greatest danger. His mantra, which he quietly recites during times of stress — "I am a leaf on the wind; watch how I soar" — has become a favourite quotation among fans.

Wash keeps a collection of plastic toy dinosaurs in the ship's cockpit and plays with them during lulls in the action. Many fans believe that he is the mandatory extension of Joss Whedon's personality that Whedon puts in his creations, like Xander Harris from Buffy the Vampire Slayer.

In the 2005 film Serenity, Wash dies near the end of the film, when a harpoon launched by a Reaver ship impales him, killing him instantly. His shipmates erect a memorial to him (it is unclear if this is a tomb, as well) on Haven. It appears from the movie's final scenes that River Tam then takes up his duties as pilot of Serenity (under the supervision of Mal Reynolds), at least in the beginning.