MicroRNAs (miRNAs) are small non-coding RNAs that can posttranscriptionally regulate gene expression by targeting messenger RNAs. During miRNA biogenesis, the star strand (miRNA*) is generally degraded to a low level in the cells. However, certain miRNA* express abundantly and can be recruited into the silencing complex to regulate gene expression. Most miRNAs function as suppressive regulators on gene expression. Group B coxsackieviruses (CVB) are the major pathogens of human viral myocarditis and dilated cardiomyopathy. CVB genome is a positive-sense, single-stranded RNA. Our previous study shows that miR-342-5p can suppress CVB biogenesis by targeting its 2C-coding sequence. In this study, we found that the miR-10a duplex could significantly up-regulate the biosynthesis of CVB type 3 (CVB3). Further study showed that it was the miR-10a star strand (miR-10a*) that augmented CVB3 biosynthesis. Site-directed mutagenesis showed that the miR-10a* target was located in the nt6818-nt6941 sequence of the viral 3D-coding region. MiR-10a* was detectable in the cardiac tissues of suckling Balb/c mice, suggesting that miR-10a* may impact CVB3 replication during its cardiac infection. Taken together, these data for the first time show that miRNA* can positively modulate gene expression. MiR-10a* might be involved in the CVB3 cardiac pathogenesis.