MicroRNAs are small non-coding RNAs with a central role in the post-transcriptional control of gene expression, that have been implicated in a wide-range of biological processes. Regulation of miRNA expression is increasingly recognized as a crucial part of the host response to infection by bacterial pathogens, as well as a novel molecular strategy exploited by bacteria to manipulate host cell pathways. Here, we review the current knowledge of bacterial pathogens that modulate host microRNA expression, focusing on mammalian host cells, and the implications of microRNAs (miRNA) regulation on the outcome of infection. The emerging role of commensal bacteria, as part of the gut microbiota, on host miRNA expression in the presence or absence of bacterial pathogens is also discussed.