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A chirped-pulse Fourier transform microwave spectrometer was used to record the rotational spectrum of methyl vinyl ketone (MVK, 3-butene-2-one) from 6 to 18.9 GHz. Two stable conformations were identified: the previously documented \textit{anti}periplanar (\textit{ap}) conformer and \textit{syn}periplanar (\textit{sp}), which is reported for the first time in this microwave study. Methyl torsional analysis with XIAM resulted in $V3$ barrier heights of 433.8(1) and 376.6(2) cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ for \textit{ap}- and \textit{sp}-MVK, respectively. Heavy atom isotopic species were detected in natural abundance allowing bond lengths and angles of the molecular frames to be calculated through Kraitchman analysis. A comparison with \textit{ab initio} calculations is included.