Primary central nervous system lymphoma (PCNSL) is a rare tumour of childhood with 15–20 cases reported yearly in North America. We present a case of a 13-year-old boy diagnosed with PCNSL who presented more than one-and-a-half years post-treatment with high dose cytosine arabinoside and methotrexate with a right-sided basal ganglia haemorrhage on MRI following a concussion while playing organised football against medical advice. There was no evidence of an underlying vascular malformation or recurrent disease by MRI, cerebrospinal fluid analysis or positron emission tomography computed tomography (PET-CT). However, 6 months post-injury he presented with asymptomatic disease recurrence of the frontal lobe. Our case reports an unusual MRI pattern of post-traumatic injury in a child previously treated for PCNSL that would support a recommendation for the avoidance of contact sports in this population.