Tobias graduated from Harvard College in 1968 with a BA in Slavic languages and literature. In 1972, he obtained his Masters of Business Administration degree from Harvard Business School.
While in business school, he wrote for New York Magazine, and after graduation became a contributing editor.
In 1973, Tobias wrote The Best Little Boy in the World, an autobiography in which he spoke of his experiences as a gay boy and young man. He published it under the pen name "John Reid" to avoid the repercussions of being openly gay; the book was republished in 1998 under his real name to coincide with a sequel, The Best Little Boy in the World Grows Up.
Although he has never held a job in the investment industry, he has written extensively on the subject, including The Only Investment Guide You'll Ever Need, The Only Other Investment Guide You'll Ever Need, My Vast Fortune, Money Angles, The Invisible Bankers: Everything the Insurance Industry Never Wanted You to Know, and The Funny Money Game. He parlayed his writings and advice into success in the software industry with his Andrew Tobias's Managing Your Money financial application.
Tobias books on other topics include Fire and Ice: The Charles Revson/Revlon Story, Getting By on $100,000 a Year, a collection of magazine pieces; Auto Insurance Alert, a book proposing radical insurance reform; Kids Say Don't Smoke on the efforts of tobacco companies to sell cigarettes to younger consumers (which was also published in Russian).
After leaving New York Magazine in 1976, he was a contributing editor to Esquire, then Playboy, Time, and Parade.
In 1999 he became treasurer of the Democratic National Committee.
He has been a strong opponent of Republican efforts to reduce taxes for high-income individuals before what he considers higher priorities.
He spearheaded a ballot initiative to convert California's auto insurance system into a no-fault system which would be paid for through a gasoline surcharge instead of premiums. He wrote a book on the topic, and funded a large part of the campaign himself.
Tobias was the partner of fashion designer and Democratic political activist Charles Nolan, who died on January 30, 2011.
Tobias was grand marshal of the 2005 New York City LGBT Pride Parade.