Accessing cerebrospinal fluid (CSF) from the craniocervical junction through the posterior atlanto-occipital membrane via cerebellomedullary injection (also known as cisternal puncture or cisterna magna injection) has become a standard procedure in preclinical studies. Such delivery provides broader coverage to the central and peripheral nervous system unlike local parenchymal delivery alone. As a clinical application, this approach offers a more reliable method for neurological gene replacement delivery in infants, where skull-mounted devices are not indicated. Here we describe a consistent, precise, and safe method for CSF injection with minimal equipment and technical skills.