Jonathan is the husband of Susan Long and the father of Jake and Haley Long. He is a normal human being who had not the slightest clue about his family's magical background, so he was unaware that their mother (though not a dragon herself) came from a family of "magical reptiles", or dragons. Jonathan works as a financial planner.
Jake went back to 1986 and revealed his family's secret to his dad. When Jonathan found out at first, he was frightened but demonstrated nobility when he refused to reveal Susan's identity to the Huntsclan. However, Jonathan was told it was all a dream and still did not know about the existence of magical creatures. Jake's reckless time-traveling was responsible for the only occasion in the series where Jonathan and the Huntsman ever met. According to Lao Shi, Jonathan, although a bit odd, is a role model the Dragon Council felt Jake should follow because he was kind, honest, and courageous.
He proved this when, after Jake was hurt, he attacked the Strigoi. He was unable to defeat them, but he distracted them long enough for Jake to destroy them. He also showed his bravery when he saved Jake from a bear. What he didn't know was that the "bear" was actually the Jersey Devil and that by defeating him, he also saved a village of sprites, who erected a statue to homage him.
Eventually, he discovered the existence of magical creatures and learned the secret about his family when he accidentally walked in on Haley in dragon form, forcing everyone to explain the truth to him, which he accepted without reservations. He then showed courage by helping Jake defeat the Shades during his battle with the Dark Dragon by discovering their weakness: light and using it to destroy them all in one go. Jake later asked him why he was so okay with all of this and he admitted that he always thought that there was something magical about his family. Presumably from his "dream", he had. He also showed how courageous he was by rushing into battle to help Jake when he found out he was in trouble, although he had only just learned the family's secret and was still trying to process that.
His habit of leaving sticky notes for his son provided a few hints, which Jake eventually found helpful in defeating a henchman of King Hammer without having to reveal himself as a real dragon by using his powers or flying away.
Once on a camping trip with Jake, Trixie, and Spud in the New Jersey Pine Barrens, he unknowingly set up camp near a village of sprites while the Jersey Devil threatened to destroy it. It was defeated by Jonathan, who mistook it for a bear. The sprites erected a statue in his honor.
When Jake grew tired of being punished for his various dragon duties, which he could not tell Jonathan about without revealing the truth of his being a dragon, he decided to go back in time to when Jonathan and Susan were still teenagers at school. Jake saw to it an undelivered letter where Susan revealed her secrets ended up in Jonathan's locker. However, he did not take the news well and broke up with Susan. To make things worse, Jonathan telephoned a radio show for advice on the air, attracting the attention of the Huntsclan, which sent the then-apprentice Huntsman on his first assignment to capture him for questioning. Jonathan bravely refused to turn Susan over to them, gaining the respect of Lao Shi. Jake, Susan, and Lao Shi rescued him, tricking him into believing the whole "dragon thing" was a dream.
Some Strigoi, magical creatures that feed on dragon blood, mistakenly believed Jonathan to be the American Dragon. Despite not being able to defeat them Jonathan impressed Jake by being able to resist more than expected. Afterward, Lao Shi informed Jake that the Dragon Council perceives Jonathan as brave and loyal and it helped them to agree into making Jake the American Dragon.
While on a family vacation in Hong King, Jonathan finally learned of his wife's family secret and helped them in defeating the Dark Dragon's Shade Demons. In the last scene, Jake is surprised that his father takes this pretty well, Jonathan responded that he guess he had always known there was something "magical" about his family, which Jake replied that he is also the same.
- Originally, it was gone to be revealed later in the series that Jonathan was a Werewolf, at an episode would've reveal that he would go on a "Business Trip" whenever the Moon was Full.
- He's the stereotypical embarrassing parent but has a strict side on his part.
- When in school, if seated in classes by the common New York Public School practice of alphabetical order, then "Luong" and "Long" would probably have been next to each other most of the time. This may have been when their relationship first began.
- He is one sixteenth Navajo Indian, making Jake and Haley part Navajo as well.