Abstract In this study, we evaluated the ability of a soil-conditioner mixture to reduce soil erosion of coastal sand dunes. Plant growth-promoting rhizobacterium Bacillus sp. SH1RP8 was isolated from indigenous plants normally found in coastal sand dunes. Potassium polyacrylate, a superabsorbent polymer, was applied as a soil-conditioner to evaluate the promotion of Arundo donax growth in sand dunes at Songjeong beach (site A) and Soongut beach (site B), South Korea. This soil-conditioner mixture increased the shoot length of A. donax cultivated for 10 months at both the sites, specifically 167.52% at site A and 122.78% at site B, whereas shoot biomass increased by 370.64% and 149.30%, respectively. The viable cell count of strain SH1RP8 was maintained during the vegetation restoration period. Soil containing A. donax lost soil at a rate of 1.61% when it was watered daily for 8 days (2 L/day), whereas the loss was 55% in the control plots. These results indicate that the soil-conditioner mixture containing SH1RP8 can serve as a promising microbial inoculant for increasing plant growth in coastal sand dune environments, and for improving the phytostabilization efficiency and preventing soil erosion.