This study evaluated the effects of biostimulants derived from Prosopis cineraria and P. juliflora on wheat (Triticum aestivum L.) germination and growth under drought stress induced by polyethylene glycol (PEG) at varying concentrations (−0.9, −1.1, and −1.3 MPa). Aqueous extracts of Prosopis species were applied at 0.5, 1, and 2% concentrations. Results showed that P. cineraria biostimulants consistently enhanced seed germination, shoot, and root growth across all drought levels, with the most substantial effects observed at higher concentrations. Conversely, P. juliflora biostimulant exhibited variable effects, providing benefits depending on the drought severity. It performed better under moderate drought stress, significantly increasing root length and shoot dry weight. At a 2% concentration, it also showed some improvement under severe drought conditions. Both biostimulants influenced the root-to-shoot length ratio, promoting root growth to mitigate drought stress. These findings underscore the potential of P. cineraria and P. juliflora extracts as biostimulants to enhance wheat growth and resilience under water-limited conditions. Optimizing biostimulant concentrations for different stress levels is essential to maximize their effectiveness in improving plant productivity.