In the present study we analyzed miRNA and mRNA expression profiles in human peripheral blood lymphocytes (PBLs) incubated in microgravity condition simulated by a ground-based Rotating Wall Vessel (RWV) bioreactor. Our results show that 42 miRNAs were differentially expressed in MMG-incubated PBLs compared with 1g-incubated ones. Among these miR-9-5p miR-9-3p miR-155-5p miR-150-3p and miR-378-3p were the most dysregulated. To improve the detection of functional miRNA-mRNA pairs we performed gene expression profiles on the same samples assayed for miRNA profiling and we integrated miRNA and mRNA expression data. The functional classification of miRNA-correlated genes evidenced significant enrichments in the biological processes of immune/inflammatory response signal transduction regulation of response to stress regulation of programmed cell death and regulation of cell proliferation. We identified the correlation between miR-9-3p miR-155-5p miR-150-3p and miR-378-3p expression with that of genes involved in immune/inflammatory response (eg. IFNG and IL17F) apoptosis (eg. PDCD4 and PTEN) and cell proliferation (eg. NKX3-1 and GADD45A). Experimental assays of cell viability and apoptosis induction validated the results obtained by bioinformatics analyses demonstrating that in human PBLs the exposure to reduced gravitational force increases the frequency of apoptosis and decreases cell proliferation. microRNA expression profiling were carried out on total RNA extracted from PBLs of twelve healthy donors at the end of 24h-incubation time in MMG and in 1g conditions. Analyses were performed by using the Human miRNA Microarray kit (V2) (Agilent Technologies) that allows the detection of 723 known human (miRBase v.10.1) and 76 human viral miRNAs. By comparing the expression profile of MMG-incubated vs. 1g-incubated PBLs of the same donor we found 42 differentially expressed miRNAs 25 up-regulated and 17 down-regulated.