The microwave spectrum of 3-butyne-1-selenol has been studied by means of Stark-modulation microwave spectroscopy and quantum chemical calculations employing the B3LYP/aug-cc-pVTZ and MP2/6-311++G-(3df,3pd) methods. Rotational transitions attributable to the (HSeCH2CH2C)-Se-80=CH and (HSeCH2CH2C)-Se-78=CH isotopologues of two conformers of this molecule were assigned. One of these conformers possesses an antiperiplanar arrangement for the atoms Se-C-C-C, while the other is synclinal and seems to be stabilized by the formation of a weak intramolecular hydrogen bond between the hydrogen atom of the selenol group and the pi electrons of the C=C triple bond. The energy difference between these conformers was determined to be 0.2(5) kJ/mol by relative intensity measurements, and the hydrogen-bonded form was slightly lower in energy.