The neutron capture cross section for the 139 La(n, γ) 140 La reaction at 0.0536 eV was measured for the first time using monochromatic neutrons coming from a Triple Axis Spectrometer at the TRIGA Mark-II reactor. The neutron beam intensity was determined by irradiating Au-monitor foil together La 2 O 3 target. The radioactivity of the products was determined via high resolution γ-ray spectrometry. The obtained cross section value is 6.13±0.3b, which is 1.34% and 0.21 % lower than that in the ENDF/B-VII and JENDL-3.3 data library, respectively.