Emily (voiced by Jules de Jongh) is a large Stirling Single tender engine.
When Emily was new to Sodor, she was ignored by the other engines for pulling Annie and Clarabel without Thomas' permission or knowledge. The matter was resolved after she saved both Thomas and Oliver from a nasty accident on the cross-points, and she was rewarded with two new coaches. Emily proved to be kind-hearted, as she was the only engine concerned about Henry when he was ill due to leaky tubes and when she stuck up for Salty when Thomas and Percy were teasing him.
However, Emily has proven to be a nuisance on occasion as she bossed everyone about when they were clearing up after a storm; Thomas when taking passengers, and Percy when shunting trucks. When pulling the express for the first time, she was determined to keep to Gordon's timing, only to run out of water.
When Thomas had to stay at Knapford Sheds, Emily did not like his company at first as she just wanted some sleep. However, she learned how comfortable it is to have the company of friends and once Tidmouth Sheds was rebuilt, she was transferred there to be with her new shedmates.
Like most engines, Emily can get quite puffed up in the smokebox. When she was called "Excellent Emily", she ignored the advice of Murdoch, Thomas, and Duck only to get herself into trouble. Afterwards, she took their advice to get her job done.
Emily tries her best to make her friends happy. When she assumed that Mavis was sad, she took flowers to the quarry, but only created a mess. When she tried to help her friends with the football match, she neglected to fetch the dirty washing, which turned out to be the football team's uniforms. Also, when Sir Topham Hatt lost his top hat, Emily went to find it without success and then took the special Christmas train without permission. However, she always makes amends for her friends' sake.
She later took Paxton to the Sodor Dieselworks after he was damaged during an accident at the Blue Mountain Quarry.
When Thomas hid his snowplough, Emily had to do Thomas' work and saved him when he got stuck in the snow.
Thomas told Emily about the "Flatbeds of Fear," but Emily did not believe in it and said there was an explanation. She eventually believed in it, until Thomas told her that it was just one of Salty's tall tales.
When the Steam Team try to clear the tracks of snow for Connor to deliver the last train for Christmas, Emily is unable to clear them from the Sodor side, but is happy to see Hiro as he clears it from the other direction, then is disappointed when they mistake Harold for Father Christmas by believing his red port lamp to be Rudolph's nose.
She was later informed by Paxton about the rumour that Toby was to be scrapped, but Henrietta overheard and knew it wasn't true. Emily took her to find Toby, and once they found him safe, Emily gave him some of her coal.
In the seventh season, Emily acts as a sisterly figure to the others. Emily is kind and friendly and always sensitive to the other engines' feelings. If she wrongs someone, knowingly or not, she is quick to apologize.
From the eighth season onwards, however, Emily can tend to get into trouble because of her fussy and bossy attitude, but she is nicer than she lets on. She seems to want to strive to be one of the best, and it sometimes causes mishaps, though she usually makes up for her mistakes when she realizes her errors.
From the seventeenth season onwards, however, her personality seems to be reverting as to how it was in the seventh season.