Heterogeneous ribonucleoproteins (hnRNPs) are involved in a variety of key cellular functions and are most likely involved in different steps of pre-mRNA processing. Over the past decades, the central roles of hnRNPs have been detected, which show that they are involved in RNA splicing, telomere biogenesis, DNA repair, cell signaling, and in transcription and translation. Mounting evidence suggests that they are involved in the regulation of mRNA stability and translation in many cancer types. The hnRNPs have a variety of potential roles in inhibition of apoptosis, angiogenesis, cell invasion, and epithelial-mesenchymal transition (EMT). It is thus suggested that hnRNP might be a novel and promising therapeutic target and a marker for treatment response and prognostic evaluation. The aims of this review are to survey the existing evidence and discuss the diverse functions of hnRNPs in cancer metastasis.