Background: Cancer is one of the top causes of mortality worldwide. The matrix metalloproteinase MMP12 is highly expressed in some cancers, but there is a lack of meta-analyses proving the correlation between MMP12 and cancer. Materials & methods: A literature search was performed using Web of Science, PubMed and other databases. Quantitative meta-analysis of the data was carried out. The Cancer Genome Atlas was further used to validate our results. Results: High MMP12 expression was associated with poorer overall survival and poorer 5-year overall survival. Elevated expression of MMP12 predicted shorter overall survival in six cancers and worse disease-free survival in four malignancies based on validation using the Gene Expression Profiling Interactive Analysis online analysis tool. Conclusion: Elevated MMP12 expression is likely a marker of poor prognosis in various cancers.