Skeletal muscle atrophy is prevalent in chronic diseases and microRNAs (miRs) may play a key role in the wasting process. miR-23a was previously shown to inhibit the expression of atrogin-1 and MuRF1 in muscle. It also was reported to be regulated by NFATc3 in cardiomyocytes. The objective of this study was to determine if miR-23a is regulated during muscle atrophy and to evaluate the relationship between calcineurin (Cn)/nuclear factor of activated T-cells (NFAT) signaling and miR-23a expression in skeletal muscle cells during atrophy. miR-23a was decreased in the gastrocnemius of rats with acute streptozotocin (STZ)-induced diabetes, a condition known to increase atrogin-1 and MuRF1 expression and cause atrophy. Treatment of C2C12 myotubes with Dexamethasone (Dex) for 48 hours also reduced miR-23a as well as RCAN1.4 mRNA, which is transcriptionally regulated by NFAT. Both NFATc3 nuclear localization and the amount of miR-23a decreased rapidly within 1 hour of Dex administration suggesting a link between Cn signaling and miR-23a. Compared to primary myotubes from wild type mice, myotubes from CnAα-/- or CnAβ-/- mice had a lower level of miR-23a. Dex did not further suppress miR-23a in the Cn-deficient myotubes. Overexpression of CnAβ in C2C12 myotubes prevented Dex-induced suppression of miR-23a. Finally, miR-23a was present in exosomes isolated from the media of C2C12 myotubes and Dex increased its exosomal abundance. Dex did not alter the number of exosomes released into the media. We conclude that atrophy-inducing conditions down regulate miR-23a in muscle by mechanisms involving attenuated Cn/NFAT signaling and selective packaging into exosomes.