This chapter explores working memory as the central cognitive deficit associated with dyslexia, emphasising its critical role in learning, reasoning, and performance. Working memory is described as a limited-capacity system responsible for holding and manipulating information over short periods. The authors differentiate between components of working memory – such as auditory and visual memory – and demonstrate how deficits in these areas can affect tasks such as reading, writing, problem solving, and conversation. Drawing from psychological theory and empirical research, the chapter discusses how working-memory inefficiencies underlie many of the behaviours and skill deficits seen in people with dyslexia. Examples include difficulty following multi-step instructions, forgetting verbal information, and being unable to manage competing demands. The authors also highlight how limitations in working memory can result in performance inconsistencies, which are often reported by clients. Assessment using tools such as the WAIS-IV helps identify these weaknesses and guide support strategies. Ultimately, this chapter reinforces the view that dyslexia is best understood not solely through academic outcomes but through an understanding of the cognitive systems that support performance – particularly working memory.