On the personal side, Tim was born in Toledo, Ohio and graduated Cahuenga High School in Los Angeles. He went on to graduate from UCLA where he majored in journalism. When the series opens he has been working on The Los Angeles Sun for 5 years and is about 27 years old.

No close relatives are ever seen, although Tim’s Cousin Harvey O’Hara and his Great-Uncle Seamus O’Hara do each show up for a visit in the course of the show.

Enjoying his bachelorhood for all it is worth, Tim has a happily successful dating career although he admits to not being ready to "settle down." Although never becoming "serious" with any one girl, he is usually drawn to intelligent women and he particularly likes redheads.

Hardly the bumbling bachelor stereotype, Tim is perfectly self-reliant doing household chores and cooking meals without a second thought, as is the Martian, although Martin takes full advantage of his powers to speed up the efficiency of the tasks, much to Tim’s approval.

In fact, Tim O’Hara completely accepts the Martian’s abilities. He admires Martin’s powers and he does not try to control or prevent their use, except when he believes that utilizing them may lead to expose the Martian’s alien identity. At times, when the pair is faced with a crisis, Tim will freely brainstorm ways that the Martian’s powers can help to solve things. And knowing the truth about the people of Mars makes Tim all the more unhappily aware of how humans tend to stereotype others. When a UFO investigator announces that he believes in a derogatory image of "green Martians", it is Tim who is clearly offended and uncomfortable with the reference, offering an apologetic look at Martin, while the Martian merely seems to accept the misnomer as the status quo concept of an ignorant society.

Not that it is always easy for Tim, having a man from Mars as a houseguest, and the reporter recognizes this, sometimes voicing loud justifiable objections to the escalatingly bizarre situations occasionally caused by the Martian’s presence, but never to the point of endangering their friendship. Tim’s unfailing sense of humor helps them both cope, and he is comfortably demonstrative in sharing his feelings towards his Martian "uncle", who he considers a member of his own family.

Tim understands the necessity of protecting the Martian’s identity and he is willing to go to great lengths, including personal sacrifice, to protect him. And while the irony of being a reporter unable to tell the greatest news story of all time does not escape Tim, he puts loyalty ahead of personal gain without regret.