Buckell attended Clarion East in 1999. Not long after that he made his first sale, "Fish Merchant", to Scott Edelman at Science Fiction Age. The story appeared in the March, 2000 issue. About the time of the sale, his story "In Orbite Medievali" won a quarterly contest for the Writers of the Future. Since then his stories have appeared in a variety of places, including the magazines Analog and Nature, and the anthologies New Voices in Science Fiction, Men Writing Science Fiction As Women, and So Long Been Dreaming.
His first novel, Crystal Rain, was published in February 2006 by Tor Books. His second novel, Ragamuffin was published in 2007, and was nominated for the illustrious Nebula award for that year. Sly Mongoose, his third novel, was published in August 2008. His first short story collection, Tides from the New Worlds, was published as a signed limited edition hardcover by Wyrm Publishing in April 2009.
Buckell made a non-physical appearance on the Who Wants to Be a Millionaire game show as a "Phone-A-Friend" for his friend Heidi Ruby Miller.
In 2008, he donated his archive to the department of Rare Books and Special Collections at Northern Illinois University.
On June 16, 2008, Tobias was announced as the author for the sixth novel in the Halo book series titled "The Cole Protocol", named after military procedures made to prevent the Covenant from obtaining crucial information, such as the location of Earth. The novel was published in November 2008.
In December, the novel debuted at #4 on the New York Times Best Seller list for paperback trade fiction. Also he wrote together with [[Karen Traviss]], [[Eric Nylund]] and many other authors the novel ''[[Halo Evolutions]]: Essential Tales of the Halo Universe'', which was released in November 2009.
In July 2010 he published an audiobook, The Alchemist and The Executioness, with Paolo Bacigalupi. These two works are to be published as separate print books in January 2011.