Background: Because detecting tumor-derived cell free DNA (cfDNA) in the blood of patients with primary or metastatic brain tumors is challenging, here we studied whether cerebrospinal fluid (CSF) could be serve as an alternative “liquid biopsy” by enabling measurement of circulating DNA within CSF to characterize tumor specific mutations. Methods: The paired cfDNA in CSF and plasma were collected from 20 patients with brain tumors and was subjected to enrichment for a 1.15M size panel cover exon regions from 1,086 genes. Followed by next generation sequencing on an Illumina X10 platform, the captured sequencing data was further processed using bioinformatics analysis to identify somatic mutations, including single nucleotide variants (SNV) and short insertions/deletions (indels). Results: The mutation profiles of 48 tumor associated genes in cfDNA were compared between the CSF and plasma. Our results showed that both average somatic mutation number and frequency identified in the cerebrospinal fluid was much higher than that in the corresponding plasma samples (25 vs. 18 & 1.39% vs. 0.55%). Among the twenty cases, one more potential actionable mutation, EGFR exon 19 deletion mutation with a 25.38% allele frequency variation, was only detected in the CSF cfDNA of a patient with brain metastasis lung cancer. Conclusions: Tumor mutations were detectable in CSF cfDNA of patients with different primary and metastatic brain tumors. Thus cerebrospinal fluid cell free DNA analysis could be a potential alternative analysis for patients with primary or metastatic brain tumors.