Objective: To identify matrix metalloproteinase (MMP)-2 and -9 in CSF from dogs with intracranial tumors. Sample: CSF from 55 dogs with intracranial tumors and 37 control dogs. Procedures: Latent and active MMP-2 and -9 were identified by use of gelatin zymography. The presence of MMPs in the CSF of dogs with intracranial tumors was compared with control dogs that were clinically normal and with dogs that had idiopathic or cryptogenic epilepsy or peripheral vestibular disease. Relationships between MMP-9 and CSF cell counts and protein were also investigated. Results: Latent MMP-2 was found in CSF samples from all dogs, although active MMP-2 was not detected in any sample. Latent MMP-9 was detected in a subset of dogs with histologically documented intracranial tumors, including meningiomas (2/10), gliomas (3/10), pituitary tumors (1/2), choroid plexus tumors (5/6), and lymphoma (4/4), but was not detected in any control samples. Dogs with tumors were significantly more likely than those without to have detectable MMP-9 in the CSF, and the presence of MMP-9 was associated with higher CSF nucleated cell counts and protein concentration. Conclusions and Clinical Relevance: Latent MMP-9 was detected in most dogs with choroid plexus tumors or lymphoma but in a smaller percentage of dogs with meningiomas, gliomas, or pituitary tumors. Detection of MMP in CSF may prove useful as a marker of intracranial neoplasia or possibly to monitor response of tumors to therapeutic intervention.