MicroRNA1511 (miR1511) is a small RNA with unknown function identified in several plants by deep sequencing. In this study, we showed that this small RNA is an authentic miRNA by analyzing the structure of the precursor stem-loop containing the newly identified miR1511* sequence. We confirmed this result by Northern blotting analysis. We used 5'RACE to identify one of the target genes (GmRPL4a) cleaved by both miR1511 and miR1511*. The site cleaved by miR1511* was located in the first exon of GmRPL4a, and the site cleaved by miR1511 was located in the second exon. The expression level of miR1511/1511* was higher in leaves than in roots and stems. In contrast, the lowest level of GmRPL4a expression was in the leaves and the highest in the root. These results indicate that an miRNA can co-regulate with an miRNA* to cleave the same target gene in plants, and that the level of GmRPL4a mRNA is regulated by miR1511/1511*.