Following previous contributions dedicated to the main isotopologue, ¹⁴NH₃, in the present work, we examine the ¹⁵NH₃ absorption spectrum between 3950 and 6350 cm ^-1 in order to elaborate an absorption line list for ammonia in natural isotopic abundance. For this purpose, several room temperature Fourier Transform absorption spectra of ammonia highly enriched in ¹⁵NH₃ measured in the 90′s and available from the Kitt Peak data centre have been analysed. In addition, a more recent high-resolution spectrum recorded in Brussels between 4150 and 4600 cm^-1 is also considered. The spectra were divided in three separate intervals (3900-4706, 4706-5650 and 5650-6350 cm^-1) for which experimental lists including 3499, 3778, and 2302 lines, respectively, were retrieved and treated independently. By comparison with an ab initio line list (the BYTe list) and systematically validating the assignments by using lower state combination difference relations (LSCD), 1763, 1355 and 426 transitions could be assigned in the three regions, respectively. They belong to 12, 13, and 7 bands and correspond to 96.3, 89.5 and 77.7 % of the intensities in the region, respectively. For comparison, only four ¹⁵NH₃ bands were previously assigned in the literature in the entire studied region. The obtained ¹⁵NH₃ assigned line lists were gathered with the previously elaborated line list of the main isotopologue to produce a recommended line list for natural ammonia between 3900 and 6350 cm -1 .