Mullard was founded in 1920 by Captain Stanley R. Mullard as The Mullard Radio Valve Co. Ltd. in Southfields, London. He had previously been involved with the design of thermionic valves for the Admiralty, and had also worked for the Z Electric Lamp Co. With the creation of the BBC in 1922 and the technical demands required, Mullard entered into a part share with the Dutch company, Philips in 1923 to aid with finances and meet these demands. In 1925, the company became Mullard Limited, a registered trade mark. Then, in 1927 due to the increasing demands, Mullard decided to sell all its shares to Philips so that it was now a wholly owned subsidiary of Philips.

From this point on, the company expanded across England. They initially had major factories in Mitcham, Surrey from 1929, but in 1938 another factory was opened in Blackburn, Lancashire. This was a joint endeavour with the local authority to combat increasing local unemployment caused by the decline of the cotton industry. This site became the company's largest valve manufacturing plant and they became a major employer in the town. The site in Blackburn remained in operation for the following five decades before finally being closed in 1982. The company had become intertwined with the identity of the town and had employed generations of people so that it now forms a significant point in the history of the area.

However, the company did have other sites across England. Further valve factories were located across Lancashire in Southport, Fleetwood and Lytham St. Annes, another factory was opened in Belmont, Durham, and further semiconductor factories were later opened in Southampton and Hazel Grove, Cheshire. The plant in Southampton was of a similar scale to that in Blackburn becoming the biggest semiconductor facility in Europe, employing 3000 people.

The company saw success over many decades, however by the 1970s, business was declining. Throughout the 1970s and early 1980s, many of its factories closed, and eventually in 1988, Philips ceased to use the Mullard name with the subsidiary being renamed to Philips Components Limited.