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Use of low-temperature IR spectroscopy in studies of compounds with a developed system of hydrogen bonds such as DL-serine revealed a complete set of vibrational frequencies. The region of manifestation of stretching vibrations of OH groups involved in the formation of strong hydrogen bonds was found. It is shown experimentally that in a crystal some of the molecules of SL-serine exist in the nonionized form. On the basis of analysis of experimental data, frequency ranges of stretching deformation and torsional vibrations of NH3+, COO−, and OH groups were determined more accurately. It is found that in the crystals there exist molecules of DL-serine with different spatial orientation of NH3+ COO−, and COH groups. It is shown that conformational diversity of molecular structures is also preserved at T=18 K.