Background Pseudoprogression in gliomas has been extensively described after radiotherapy with or without chemotherapy, but not after chemotherapy alone. Here we describe the occurrence of pseudoprogression in patients with anaplastic oligodendrogliomas treated with postoperative procarbazine, lomustine and vincristine (PCV) chemotherapy alone. Methods We retrospectively reviewed the medical and radiological files of patients with 1p/19q codeleted, IDH‐mutant anaplastic oligodendrogliomas treated with PCV chemotherapy alone who presented magnetic resonance imaging (MRI) modifications suggestive of tumour progression and in whom the final diagnosis was a pseudoprogression. Results We identified six patients. All patients underwent a surgical resection and were treated with PCV chemotherapy without radiotherapy. After a median of 11 months following the initiation of chemotherapy (range: 3–49 months), the patients developed asymptomatic white matter MRI modifications around the surgical cavity leading to the suspicion of a tumour progression. These modifications appeared as hyperintense on T2‐fluid‐attenuated inversion recovery (FLAIR) sequence, hypointense on T1 sequence, and lacked mass effect (0/6), contrast enhancement (0/6), restriction on diffusion‐weighted imaging (0/4), relative cerebral blood volume (rCBV) increase on perfusion MRI (0/4), and hypermetabolism on 18F‐fluoro‐L‐dopa positron emission tomography (18F‐DOPA PET) scan (0/3). One patient underwent a surgical resection demonstrating no tumour recurrence; the five other patients were considered as having post‐therapeutic modifications based on imaging characteristics. After a median follow‐up of 4 years all patients were progression‐free. Conclusions Anaplastic oligodendroglioma patients treated with postoperative PCV chemotherapy alone occasionally develop T2/FLAIR hyperintensities around the surgical cavity that can wrongly suggest tumour progression. Multimodal imaging and close follow‐up should be considered in this situation.