Funder: Great Ormond Street Hospital Children's CharityFunder: Blood Cancer UK Bennett FellowshipFunder: Biomedical Research Council FellowshipSummary: T‐cell ALL (T‐ALL) is an aggressive malignancy of T‐cell progenitors. Although survival outcomes in T‐ALL have greatly improved over the past 50 years, relapsed and refractory cases remain extremely challenging to treat and those who cannot tolerate intensive treatment continue to have poor outcomes. Furthermore, T‐ALL has proven a more challenging immunotherapeutic target than B‐ALL. In this review we explore our expanding knowledge of the basic biology of T‐ALL and how this is paving the way for repurposing established treatments and the development of novel therapeutic approaches