The fragile X mental retardation protein (FMRP) is an RNA binding protein that has an essential role in neurons. From the soma to the synapse, FMRP is associated with a specific subset of messenger RNAs and controls their posttranscriptional fates, i.e., dendritic localization and local translation. Because FMRP target mRNAs encode important neuronal proteins, the deregulation of their expression in the absence of FMRP leads to a strong impairment of synaptic function. Here, we review emerging evidence indicating a critical role for FMRP in the control of mRNA stability. To date, two mRNAs have been identified as being regulated in this manner: PSD-95 mRNA, encoding a scaffolding protein, and Nxf1 mRNA, encoding a general export factor. Moreover, expression studies suggest that the turnover of other neuronal mRNAs, including those encoding for the GABA(A) receptors subunits, could be affected by the loss of FMRP. According to the specific target and/or cellular context, FMRP could influence mRNA stability in the brain.