The Sandman writer, who stepped down from the charity's board of directors earlier this year, pledged the funding to bolster its education programme.
"I've supported the Comic Book Legal Defence Fund, initially through fundraising and awareness raising and then as a member of the board of directors, for over twenty years now," said Gaiman.
"The CBLDF has, through that time, grown from a one-person organisation dealing with emergencies that would have wiped out creators and retailers to what it is now: a major force in fighting censorship and preserving First Amendment liberties for those of us who read, create, publish or sell comics on paper or on the web."
The funding will be invested into educating readers, retailers and industry professionals about the dangers of censorship and provide sponsorship for the Kids' Right to Read Project, Banned Books Week and the new Manga: Introduction, Challenges and Best Practices publication for parents and teachers.
"He has always been the most ardent voice for the Fund being a proactive education organisation, and with this contribution, we are able to build upon the foundation he built to deliver an even more powerful programme. We are grateful to him and the Gaiman Foundation for their generous support. It will help us make a real difference."
The Gaiman Foundation, run by Neil Gaiman, his wife Amanda Palmer and their children, was awarded tax exempt status earlier this year.