Soybean (Glycine max L) is a very important legume in the human diet as well as fodder crop. Previous studies have reported that co-inoculation with PGPR (plant growth-promoting bacteria) and rhizobia promotes symbiotic nitrogen fixation efficiency, increases plant nitrogen content and reduces the occurrence of soybean diseases, thus reducing pesticide use, and protecting the environment. The aim of this study was to determine the impact of co-inoculation of soybean seeds with different strains of nodule bacteria Bradyrhizobium japonicum as well as PGPR (Pseudomonas fluorescens). Indigenous strains of beneficial bacteria used in this research were isolated from different locations in Croatia. Isolates were identified by performing 16S rRNA gene sequencing. The application of different strains of nodule bacteria resulted in a statistically justified effect on all investigated properties, with the exception of root length. A positive influence of P. fluorescens on the increase in shoot dry weight was observed with the co-inoculation with the reference strain B. japonicum and two indigenous strains. The application of P. fluorescens did not show statistically justified differences in any of the investigated properties. Co-inoculation of nodules and PGPR bacteria is a very important biotechnological tool in agriculture, which is why research in this area should definitely be continued and expanded to a larger number of P. fluorescens strains. Keywords: beneficial association, symbiotic efficiency, PGP bacteria, Pseudomonas fluorescens, Bradyrhizobium japonicum Soja (Glycine max L) je vrlo vazna mahunarka u ljudskoj prehrani te kao krmna kultura. Prethodna istrazivanja pokazala su da ko-inokulacija s rizobijama i PGPR-om (bakterijama koje poticu rast bilja, engl. Plant Growth Promoting Rhizobacteria) potice ucinkovitost simbiozne fiksacije dusika, povecava sadrzaj dusika u biljkama i smanjuje pojavu bolesti soje, cime se smanjuje upotreba pesticida i stiti okolis. Cilj ovih istrazivanja bio je utvrditi utjecaj koinokulacije sjemena soje razlicitim sojevima kvrzicnih bakterija Bradyrhizobium japonicum kao i bakterijama koje poticu rast biljaka (PGPR) (Pseudomonas fluorescens). Autohtoni sojevi korisnih bakterija koristeni u ovom istrazivanju izolirani su s razlicitih lokacija u Hrvatskoj. Izolati su identificirani sekvenciranjem 16S rRNA gena. Primjena razlicitih sojeva kvrzicnih bakterija rezultirala je statisticki opravdanim ucinkom na sva ispitivana svojstva, izuzetak je bila duljina korijena. Pozitivan utjecaj P. fluorescens na povecanje mase suhe tvari nadzemnog dijela biljke uocen je kod koinokulacije s referentnim sojem B. japonicum i dva autohtona soja. Primjena P. fluorescens nije pokazala statisticki opravdane razlike ni za jedan od ispitivanih svojstava. Koinokulacija kvrzicnih i PGPR bakterija vrlo je vazan biotehnoloski alat u poljoprivredi, zbog cega istrazivanja u ovom podrucju svakako treba nastaviti i prosiriti na veci broj sojeva P. fluorescens. Kljucne rijeci: korisne asocijacije, simbiozna ucinkovitost, PGPR bakterije, Pseudomonas fluorescens, Bradyrhizobium japonicum Soybean (Glycine max L) is a very important legume used for human nutrition as well as fodder crop. Soybean-rhizobia symbiotic nitrogen fixation has been of considerable significance for improving agricultural productivity. Plant growthpromoting rhizobacteria (PGPR) are particularly important in agricultural systems, and previous studies have reported that co-inoculation with PGPR and rhizobia enhances rhizobial colonization of the legumes, increases the number of nodules, improves the nitrogen fixation efficiency and increases plant nitrogen content. The co-inoculation with PGPR and rhizobia can reduce the occurrence of soybean diseases, thus reducing pesticide use, improving yield, and protecting the environment. PGP rhizobacteria consist of numerous genera with Pseudomonas, Bacillus and Azospirillum being the most represented. The aim of this research was to determine if the co-inoculation of soybean with Bradyrhizobium japonicum and Pseudomonas fluorescens strains can additionally improve seed yield and macronutrient uptake, compared to rhizobial inoculation alone. For this purpose, soil samples were taken from the arable horizon of different locations in Croatia and chemical properties of the soils were determined. Rhizobia strains were isolated following the trap host method and 16S rRNA gene sequencing was performed in order to identify rhizobia. Two-factorial vegetation experiment was set up in a growth chamber using a random block arrangement scheme in three repetitions and factors included different strains of rhizobia and PGPR bacterium P. fluorescens. In the full flowering phase, the number of nodules per plant, nodules dry matter weight and the shoot dry weight were measured. The influence of P. fluorescens on improving the growth of soybean plants was determined by measuring the root length. Statistical analysis was performed using the software package SAS 9.4 for Windows. Regardless of the dominance of the acidic soils, rhizobial strains were isolated from all soil samples. All tested strains were able to establish a symbiotic relationship with the soybean variety used. The highest number of nodules per plant was determined using strain B4. This strain, together with B3 resulted in the most effective infection and nodulation. Applying strains B5 and B6 in combination with P. fluorescens resulted in an increase in the number of nodules, which can be attributed to the positive effect of this PGP bacterium, although the differences were not statistically significant. The nodule dry matter weight per plant was significantly higher while using strain B4 compared to the other strains. A positive influence of P. fluorescens on the increase in shoot dry weight was observed with the co-inoculation with the reference strain B. japonicum 344 and strains B5 and B6. The greatest root length was recorded with the application of strain B3, although there were no statistically justified differences in root length. In the case of some strains, co-inoculation with PGPR bacteria led to a reduction in the number of nodules, shoot dry weight and nodule dry matter weight. Such results indicate the occurrence of competition between the strains of B. japonicum and P. fluorescens. The obtained results also indicate the need for further testing with more included strains of these beneficial bacteria.