Whilst merchandise for The Railway Series books by Wilbert Awdry was produced alongside the books, since the original broadcast of its television adaptation Thomas & Friends in 1984 in the United Kingdom, much more merchandise was produced for the television series. Large numbers of manufacturers have sought to produce items based on the Thomas & Friends franchise after the original television series was broadcast in the United States and Japan.

The most popular and wide-ranging merchandise are models of the characters, some including accompanying railway systems. Other popular products include videos, books and magazines, computer and video games, audiobooks, annuals, colouring and activity books, jigsaw puzzles, board games, stationery, clothing, cutlery, household items such as curtains, duvet covers and lampshades and soft drinks.

Thomas & Friends ranked number one in the preschool toys category in the U.S. and made the top 10 for the entire U.S. toy industry in 2010. In January 2011, Thomas & Friends ranked as the number-one preschool toy property in the U.K. for the 11th year in a row. Thomas is also a top-selling toy property in Australia, Germany, Japan and Korea. While the total traditional toy industry in the United States increased 1.9 per cent in 2010, overall Thomas & Friends toy sales increased over 47.1 per cent.

Companies Pre-Cut Model Engine Book The first commercial models released alongside The Railway Series, in 1957, were 'Pre-cut Model Engine Books'. These were full-colour printed cardboard kits whose pieces could be pressed out, folded, and glued together to make fairly realistic models. They were produced through the 1960s. Four titles were published: "Thomas, with Annie the Coach" "Percy, with Clarabel the Coach" "Gordon the Big Engine and his Tender" "James the Red Engine and his Tender" The advertisements on the back of the Railway Series books promised, "Other models are being prepared", although, even if ever prepared, they were likely never published as those 4 titles are the only ones that are known of.

A 12-page Thomas the Tank Engine Press-out Model Book () by Wilbert Awdry and Ken Stott, was released in September 1987.

In 1994, a new range of press-out models was released (, this time drawn by Ken Stott instead of C. Reginald Dalby. Each book came with various accessories including station staff, and a press-out of Tidmouth Station. The range consisted of Thomas and numerous other trains in the series.

Meccano In 1967, Meccano Ltd released a train set featuring a clockwork model of Percy the Small Engine with some trucks—a yellow open wagon and a red closed van—and a circle of blue track. The model of Percy was a fair likeness of the pictures in the books and was about the size of an O gauge engine. The box featured special artwork by Peter Edwards and included the title, "Percy the Small Engine, brought to life by Meccano".

The plastic track was advertised as: "Gauge O track that clicks together and includes Brake Rail for automatic braking. Rails specially designed to make it easy to put the train on the track." In practice, although it was advertised as 'Gauge O', this only indicated the size of the model, since the track design was not compatible with anything else (the models were effectively 'flangeless').

Adverts for the set, which showed the model train 'emerging' from the book Percy the Small Engine, appeared in Meccano Magazine and on the back of the dust-covers for several of The Railway Series books in print at the time.

The train set was only produced in 1967, and is now extremely rare. It is notable as the last O Gauge train to be made at Meccano's famous Binns Road factory in Liverpool, where the Hornby tinplate trains were made.

Photographs of the set and the adverts may be found here and a close-up of Percy may be found here.

Ertl Company

Ertl was the first company to manufacture Thomas the Tank Engine & Friends characters and sets from 1984 in the UK and from 1989 in the US. Production ceased for the US market in 2002, and for the UK market in 2005 after RC2 Corporation acquired Ertl and discontinued the ranges to avoid conflict with the then existing Thomas license held by Learning Curve Brands, which produced the similar Take Along Thomas & Friends system.

Die-cast range The most notable of the Ertl Company's Thomas ranges was a line of die-cast models and playsets. The range was very popular in the UK, and the nature of the subject matter encouraged collecting.

Thomas, Henry, and James were the first models to be released. The original Thomas featured a decal sticker sheet which allowed him to have different expressions. Percy, Toby, Annie and Clarabel, and Bertie followed in late 1985, with updated versions of Thomas, Henry, and James with red buffer beams to replace the older white ones. Edward and Gordon came out in 1988. In 1990, characters were updated with fixed plastic faces as the "sticker-face" models were prone to losing their faces. New vehicles were produced on a near-yearly basis, such as recently introduced characters to tie-in with their Television series appearance, as well as characters who had only appeared in The Railway Series books. In later years, special vehicles were created, such as metallic variants of engines, a Gold Thomas to celebrate the 50th Anniversary of The Railway Series, and a Millennium Silver Thomas in 2000.

The vehicles first used pin hook couplings to couple up and create trains. Locomotives had a moulded coupling 'eye' at each end, while rolling stock had one 'hook' coupling and one 'eye' coupling on the other end. In 2002, the vehicles were updated to use U-hook couplings, with less 'give', but they were more prone to breakage. The majority of locomotive models and some road vehicles had a diecast metal body with a moulded plastic chassis and plastic wheels. The bodies were fully painted and lined. They were free-wheeling although the chassis was rigid (locomotives were not fitted with separate bogies), and a steam locomotive's tender was part of the same moulding as its body. Models of coaches and trucks were assembled from self-coloured plastic mouldings, with some surface detail (such as coach sides) being applied using self-adhesive labels.

Sets and destinations were produced for the vehicles. The original playsets composed of playmats with illustrations of scenery and rails and moulded destinations. Later sets consisted of a grey connectable track system, with additional add-on destinations and pieces of track included with engines. The track system was updated in 2002 with detailed rail stickers and a green border.

The Ertl die-cast range was discontinued in the United States in 2002 and other parts of the world in 2005. It was effectively replaced by Learning Curve's Take-Along range.

Thomas Mini World Miniatures was a Thomas line released in 1991. It featured main characters with sticker faces which were previously used in the die-cast range. Included with the character was a connectable block base in the form of a destination, such as a turntable, windmill, level crossing, or viaduct, made from plastic components to insert into the base, and an indented track section which requires adhesive stickers to be placed. The destinations can be connected to form a playset. Characters were sold in multi-packs of three. The range was discontinued in 1995. The engines were also re-released as Keyrings.

In 2002, the line was re-released and rebranded as Thomas Mini World. The characters were updated with moulded faces, and the bases were updated to a style similar to Lego, where the track pieces and buildings can be placed in different positions.

Gold Rail Series Gold Rail Series was a Thomas line released in 1993. The products were from the Thomas Engine Collection Series made in Japan by Bandai only with coupling rods being removed. The vehicles have magnetic couplings which can connect to other vehicles using a connected switch. The playsets have a moulded section for track with self-adhesive labels for detail, have ramps on the edges for the engines to exit the destination, and feature detailed trackside accessories.

Large versions Large Motorized versions of Thomas and Percy were released in 1985. These used the same designs as the die-cast versions, and can move when pulled back. A Remote Control Thomas and a Personalized Money Box was also released in 1985, similar in design to the Motorized version. They were discontinued shortly after.

Wind-Up versions A range titled Pull Back and Go! featuring pullback versions of Thomas, Percy, Toby, and Bertie were released under Shining Time Station. A large wind-up Sir Topham Hatt was also produced, and later a Wind-Up series with Thomas, Percy, James, Henry, Bill, Ben, and Bertie.

Collector Cards Sets containing eight collector cards of vehicles were made from 1996 to 1999, similar to the existing cards on the packaging design from those corresponding years which could be cut out.

Merit

Merit produced several push-along toys to tie-in with the TV series. These included a sit-on Thomas built for toddlers which had a black handle on the rear which enabled it to be pushed along by the parent, large push along versions using hook couplings of Thomas, Annie, and Clarabel and Percy with Troublesome Trucks, a small push along version of Thomas, Annie, and Clarabel using stronger pivot couplings, a Thomas toy with shaped holes and a set of blocks which could be inserted into the correct holes on the Thomas, and some larger scale battery-operated toys.

Hornby Railways In 1985, Hornby Railways produced a series of 00 gauge model engines, track, accessories, and sets, based on Thomas & Friends, designed to be compatible with other Hornby trains, thus allowing an easy migration to more prototypical modelling. The range mainly utilised modified versions of existing Hornby engines, rolling stock and lineside accessories. Over the following years, the range expanded to include some of the main characters and rolling stock as well as train sets. During the 1990s, very few new products were made, and some vehicles discontinued. Some characters were gradually reintroduced towards the end of the decade, and more new items including major and minor characters were released from 2000. New sets were also made using a themed radio control operating system and a Trak-Mat system that sets in Hornby's existing lines used, were customers are encouraged to buy additional track packs, scenery packs, and other scenic materials to create the full printed layout. In 2005, the range revamped due to the 60th Anniversary of The Railway Series and two characters only seen in the book series were introduced, Flying Scotsman and Bear. Several pieces of rolling stock, most seen in Season 8 were also introduced, including a circus series with a total of twelve wagons, as well as three tents and stalls. The sets were redesigned using the regular analogue controllers, and a range of resin buildings seen in the television series designed for adult collectors were introduced. New items were introduced during the next three years to tie in with recent seasons of the television series and the special, The Great Discovery. In 2008 and 2009, new sets were made with the updated Midi-Mat system, replacing the Trak-Mat. From 2010, more items were again discontinuing due to their poor sales. The range was retired in 2014, but was relaunched in December 2015, albeit with only Thomas, Edward, Henry, Gordon, James, and Percy as locos, and limited rolling stock consisting of Troublesome Trucks, Annie and Clarabel, freight wagons, and James and Gordon's coaches. The other parts of the range were not reintroduced due to declining sales. The range was discontinued permanently in 2018 due to changing safety regulations.