The cytoplasm is highly compartmentalized, but the extent of subcytoplasmic mRNA localization in non-polarized cells is largely unknown. We used fluorescent particle sorting to determine mRNA enrichment in three unenclosed cytoplasmic compartments: the canonical rough endoplasmic reticulum (CRER), the TIS granule-associated rough endoplasmic reticulum (TGER), and the cytosol. Focusing our analysis on non-membrane protein-encoding mRNAs, we observed that 53% have a unique subcytoplasmic localization pattern which is determined by a combinatorial code of 3′UTR-bound RNA-binding proteins. Compartment-enriched mRNAs differed in production and degradation rates and the expression levels and functional classes of their encoded proteins. The TGER domain enriches mRNAs that encode transcription factors, the CRER highly expressed proteins, and the cytosol unstable mRNAs. The rough ER environment is stimulatory as redirecting cytosolic mRNAs to the ER increases their protein expression by two-fold, independently of the bound RNA-binding proteins. We show that local translation environments functionally compartmentalize the cytoplasm.