This was the first Cyberman story since Revenge of the Cybermen (1975), as producer John Nathan-Turner wanted to bring back an old enemy, but resisted using the Daleks. Before the title was changed to Earthshock, Nathan-Turner was adamant about keeping the return of the Cybermen a secret. He instructed Eric Saward not to have any reference to the Cybermen in the story's title. Nathan-Turner even had the studio observation galleries closed for the duration of recording and turned down an offer from Radio Times to provide advance publicity of the Cybermen on their cover. The success of this convinced Nathan-Turner to continue to mine the series' past continuity for ideas and old enemies.
Costume designer Dinah Collin was assigned the task of bringing the Cybermen into the Eighties, and worked on the project with Richard Gregory of effects firm Imagineering. They decided to abandon the rubber diving suits which had previously been the basis of the Cyberman outfit, opting instead of the more high-tech look of army G-suits. At John Nathan-Turner's suggestion, the jaws of the updated Cybermen were left clear so that the actors' mouths could be seen. The producer felt that this would reinforce the notion that the Cybermen had once been human. In a similar vein, Collin and Gregory considered leaving the Cybermen's hands bare - as had been the case in their first appearance in The Tenth Planet - and then seamlessly integrating the flesh with the Cyberman's "metallic" arm. However, it was ultimately decided that this effect would be too complex to achieve. Collin also wanted to do away with the "handlebars" on the sides of the Cyberman helmets, but this was vetoed by Nathan-Turner and Eric Saward, who felt that they were an essential part of the Cyberman image.
Although credited as script editor, Antony Root in fact did little or no work on Earthshock. He was credited to avoid Eric Saward, who had by this time replaced him in the job, being credited as such on his own work, which contravened BBC regulations.
This story replaced a script called The Enemy Within by Christopher Priest. story idea dealt with the 'secret' of what actually powered the TARDIS, in this case fear. Somewhere hidden inside the TARDIS was the one being the Doctor feared above all others, and the psychic tension between the two of them produced the energy to move through space and time. The story involved the Doctor having to confront and ultimately defeat this fear and was designed to write out the character of Adric. This was deemed unusable.
The cast didn't enjoy working with the director Peter Grimwade. According to Peter Davison, he didn't enthuse anyone. However, writer Eric Saward has said that Grimwade did lift the production by directing it with pace and a good visual eye. Steven Moffat has singled this serial out as a "really well directed show" from the series' original run which pushed the limits of what could be done in a multi-camera studio.
In post-production, Peter Grimwade became very unhappy with the incidental music composed by Malcolm Clarke, which largely relied on natural metallic sounds such as hammers striking girders. The director complained to John Nathan-Turner about the score, but because no time remained for a replacement to be created, it was decided to retain Clarke's composition. However, Eric Saward was very happy with the score, which he said added another dimension to the story.
The Cyberscope prop was built using parts the modelmaker had scavanged from the Nostromo set constructed for Alien (1979). Similarly, the digital readouts on the device flash up a random series of numbers which were also seen on the monitors of the Nostromo set.