His name is an onomatopoeic representation of the braying sound made by a normal donkey, usually represented as "hee haw" in American English: the spelling with an "r" is explained by the fact that Milne and most of his intended audience spoke a non-rhotic variety of English in which the "r" in "Eeyore" is not pronounced as /r/.

In Ernest H. Shepard's illustrations, he appears to be about chin-high to Pooh and about hip-high to Christopher Robin.

He has a long, detachable tail with a pink bow on the end, of which he is very fond, but which he is also prone to losing (Owl once mistakes it for a bell-pull).

Nevertheless, he spells his own name "eoR" when signing the "rissolution" (resolution) that the animals give Christopher Robin as a farewell present in the final chapter.

Eeyore has a poor opinion of most of the other animals in the Forest, describing them as having "No brain at all, some of them", "only grey fluff that's blown into their heads by mistake" (from chapter 1 of The House at Pooh Corner).

He lives in the southeast corner of the Hundred Acre Wood, in an area labeled "Eeyore's Gloomy Place: Rather Boggy and Sad" on the map in the Winnie-the-Pooh book.

Eeyore is also surprisingly good at the game Poohsticks, winning more times than anyone else when it is played in the sixth chapter.

Eeyore appears in the Winnie the Pooh cartoons produced by The Walt Disney Company.

His pessimistic outlook was also shown in an encounter with Piglet, who cheerfully bade him "Good morning!"

Despite their opposite personalities, Eeyore's passive nature and Tigger's optimism and outgoingness help them to accept each other's flaws and understand each other better.

In the beginning of the 2023 horror film Winnie-the-Pooh: Blood and Honey, Eeyore was killed while the other animals were starving after Christopher Robin left for college.