The objective of the paper was to estimate the impact of infrared rays heating of grass pea seeds on the protein solubility in KOH, content of fibre fraction: NDF (neutral detergent fibre), ADF (acid detergent fibre) and ADL (acid detergent lignin) and the content of carotenoids. Grass pea seeds (Lathyrus sativus L.), of Derek variety constituted the research material. The investigated seeds were heated by infrared rays in the temperature of 180ºC in the time: 30, 60, 90, 120 or 180 s. It was found out that the used thermal treatment did not have a significant impact on the protein solubility in KOH. After 180 s of heating this parameter was above 95%. Heating with infrared rays caused changes in the content of the fibre fraction in grass pea seeds. As a result of the process, the content of the NDF fraction was reduced and the growth of ADF and ADL was reported. Heating grass pea seeds with infrared rays did not cause the decrease of the carotenoids content.