The aim of this investigation was to improve salt tolerance abilities prior to rice crop harvesting, including proline accumulation, pigment stabilization, water use efficiency (WUE), photosynthetic efficiency, and growth, by using exogenous foliar-sprayed glycinebetaine (Glybet). Pathumthani 1 (PT1) is reported to be a salt-sensitive cultivar and it was selected as a model plant. The proline content of PT1 rice was enriched by 50 mM of foliar-sprayed Glybet, thereby maintaining WUE and pigment stabilization, leading to high photosynthetic performance in chlorophyll a fluorescence and CO2 assimilation, and increasing plant height when the plant was exposed to 150 mM of NaCl salt stress. The photosynthetic abilities in plants undergoing Glybet application were positively related to seed fertility percentage, leading to improved seed grain under salt stress conditions. In addition, the overall performance, i.e. that of pigments, chlorophyll a fluorescence, photosynthetic abilities, and growth characters of PT1 rice treated with 200 mM of Glybet, was inhibited with this extreme dosage. Exogenous foliar-applied Glybet in optimum doses should be used as a short-term technique for the improvement of salt tolerance in rice.