Drift from herbicides in fields adjacent to non-target crops, together with waterlogging can be detrimental to lettuce (Lactuca sativa L.). The objective of the study was to determine physiological responses of lettuce plants to exposure to glyphosate and waterlogging. Lettuce plants were subjected to treatments of combinations of foliar applications of glyphosate (45 g a.e.·ha−1) and waterlogging, and a treatment with drainage condition. Herbicide in conjunction with waterlogging, and waterlogging alone, reduced accumulation of total dry matter and leaves, as was net photosynthesis related to stomatal closure, photosystem II damage, and loss of membrane stability. Application of low doses of glyphosate on waterlogged plants favored accumulation of dry mass in the root that may be related to increase in carbohydrates to produce energy under low oxygen availability, these results indicate possible hormesis in lettuce plants to glyphosate and could be useful to reduce waterlogging damage in lettuce plants.