Salinity is one kind of abiotic stress that hinders crop productivity, especially in the coastal region. The present study focused on the salinity-tolerance of a bacterial isolate identified as Enterobacter sp. based on 16S rRNA gene sequencing and its growth-promoting potential in the rice cultivar MTU1010 (a high-yielding, short-duration variety) under the salinity stress. The isolate could tolerate NaCl up to 900 mM, but increased cell size was observed under the salinity stress. It was sensitive to neomycin and streptomycin at 100 ppm concentration and positive for indole acetic acid, siderophore, and amino-cyclopropane carboxylate deaminase production. The results of greenhouse experiments revealed that the isolate KUSP04 inoculation increased rice seed germination rate, and bacteria inoculation in the potting soil promoted the shoot and root fresh weight by 96.26% and 25.32%, and shoot and root length by 37.75% and 35.42%, respectively as compared to the control set. KUSP04 inoculation mitigated any adverse effects of salinity stress, and increments of shoot and root fresh weight 137.44% and 427.20%, and shoot and root length 36.14% and 47.78%, respectively, were observed under 100 mM salinity level as compared to their uninoculated counterparts. In addition, the inoculation improved the chlorophyll content of the tissues of the rice seedling and reduced oxidative stress by expressing antioxidant enzymes like ascorbate peroxidase and catalase and reducing the proline content of the inoculated plants. All the data suggested that Enterobacter sp. KUSP04 could be potentially used as a bio-inoculant in salinized agricultural lands to increase rice productivity.