The gas phase structure of n-propyl acetate was determined using molecular beam Fourier transform microwave spectroscopy from 2 to 40 GHz supplemented by quantum chemical calculations. The experimental spectrum revealed only one conformer with trans configuration and C1 symmetry. Torsional splittings occurred for each rotational transition due to the internal rotation of the acetyl methyl group with a barrier height of approximately 100 cm−1. The XIAM and BELGI-C1 codes were applied to reproduce the spectrum within the measurement accuracy. This investigation on n-propyl acetate has accomplished our studies on saturated linear aliphatic acetates CH3COOCnH2n+1 (n = 1–6).