The effects of smoke solutions derived from wheat straw on the germination, seedling growth characteristics, and biochemical content of grass pea (Lathyrus sativus L.) were examined in this study. The smoke solutions were applied to petri and pot media at different concentrations. Both experiments were conducted in a randomized plot design with 3 replications. In the pot experiments, the smoke solutions were applied through the initial irrigation at 5 different concentrations (1%, 5%, 10%, 20%, and 40%) while 6 concentrations were used for petri experiments (0.5%, 1%, 2%, 4%, 8%, 10%) and results were compared to a control (distilled water). The smoke solutions increased root and shoot growth but decreased the germination rate and speed of grass pea in both media. In general, there were positive outcomes for the investigated traits with moderate concentrations of solution, but negative outcomes with low and high concentrations. The smoke solution treatments improved the shoot dry weighs, K, and protein contents, but decreased the acid detergent fiber and neutral detergent fiber contents and the toxic component oxalyldiaminopropionic acid (ODAP). Accordingly, the smoke solutions stimulated the development of grass pea and promising outcomes were achieved in terms of high protein and low ODAP contents, which are the main targets of grass pea breeding studies. It was concluded, based on the present findings, that smoke solutions derived from wheat straw could be used as an environmentally friendly practice in grass pea culture to increase yield and quality. However, it should be kept in mind that concentration was a critical issue for ensuring the expected outcomes.