Background: Cognitive behavioural therapy (CBT) can be helpful for many people who experience psychosis; however most research trials have been conducted with people also taking antipsychotic medication. There is little evidence to know whether CBT can help people who choose not to take this medication, despite this being a very frequent event. Developing effective alternatives to antipsychotics would offer service users real choice. Aims: To report a case study illustrating how brief CBT may be of value to a young person experiencing psychosis and not wishing to take antipsychotic medication. Method: We describe the progress of brief CBT for a young man reporting auditory and visual hallucinations in the form of a controlling and dominating invisible companion. We describe the formulation process and discuss the impact of key interventions such as normalising and detached mindfulness. Results: Seven sessions of CBT resulted in complete disappearance of the invisible companion. The reduction in frequency and duration followed reduction in conviction in key appraisals concerning uncontrollability and unacceptability. Conclusions: This case adds to the existing evidence base by suggesting that even short-term CBT might lead to valued outcomes for service users experiencing psychosis but not wishing to take antipsychotic medication.