We report a rare paediatric case of post-dural puncture headache (PDPH) with delayed onset and atypical interscapular pain. An adolescent boy was admitted with headache and vomiting following Mycoplasma pneumoniae infection. On hospital day 2, lumbar puncture (LP) revealed clear cerebrospinal fluid (CSF) with mild pleocytosis, confirming the diagnosis of M. pneumoniae meningitis. His symptoms improved, and he was discharged on hospital day 6. On LP day 6, he developed recurrent headache with interscapular pain aggravated by movement. Whole-spine MRI on LP day 10 demonstrated a dorsal epidural CSF collection extending from Th1 to L5 with the floating dural sac sign, consistent with PDPH. He was managed conservatively and recovered fully. Follow-up MRI confirmed marked reduction of the CSF collection with improvement of spinal cord displacement. Extensive CSF spread is uncommon in children, and early whole-spine MRI is valuable in atypical cases of PDPH.