In recent years, the landscape of horticulture has undergone a transformation characterized by a reduction in cultivation area and a simultaneous surge in intensive production. This shift has been driven by the integration of cutting-edge technological innovations, with a notable emphasis on biofertilization techniques aimed at enriching soil nutrients. Within this context, our current study explores the efficiency of a novel biofertilizer originated from the synergy between Macrocystis pyrifera algal extracts and the plant growth–promoting bacterium Azospirillum argentinense. This study is focused on assessing the potential of this biofertilizer to enhance germination and the establishment phase of prevalent horticultural species, including tomato, lettuce, radish, chicory and cabbage. The seeds of the five species were inoculated and placed in germination trays in a growth chamber to evaluate germination and early seedling growth. The results showed a positive effect of the combined use of both biofertilizers on germination in lettuce, radish and chicory, where the co-inoculation produced significant differences. Moreover, early growth parameters were significantly improved in all the horticultural species studied, mainly with the combination of A. argentinense and algal extract. From the results obtained arise that the use of M. pyrifera algal extract is an interesting tool for agriculture that may improve the general plant growth and to provide stress protection. Moreover, a new biofertilizing formula is obtained when A. argentinense is combined with the algal extract, with promising effects on germination and early growth in the horticultural species used in this study.