The study was proposed to assess the efficacy of endophytic nitrogen (N)-fixing bacterial strains of Burkholderia tropica L-VT08c and Enterobacter cloacae N-VT01 on ameliorating soil features, and characteristics of pineapples on the acid sulfate soil in Vi Thanh city, Hau Giang province, Vietnam. The experiment was conducted with two factors. Therein, the first factor was N fertilizer doses: 25% N, 50% N, 75% N and 100% N; the other one was supplementations of endophytic N-fixing bacteria: no application of bacteria, individual application of the L-VT08c strain, individual application of the N-VT01 strain and a combination of both strains. Supplying the mixture of B. tropica L-VT08c and E. cloacae N-VT01 did some improvements in soil properties, including concentrations of NH₄⁺, NO₃^- and available phosphorus, and bacterial densities (7.30, 2.20 mg kg^-1 and 12.3 mg P kg^-1, and 4.01 MPN g^-1 DSW), in N uptakes (52.1 kg ha^-1), in growth as the plant height (6.80 cm), leaves number per plant (7.80 leaves plant^-1), D-leaf size (4.90 long and 0.56 cm wide), and stem size (4.30 long and 0.32 cm wide), in productivity as the fruit size (2.20 long and 0.54 cm wide) and yield (3.70 t ha^-1), and in fruit qualities as the degree Brix (0.80%) and vitamin C content (2.80 mg 100 g^-1), in comparison with the no bacteria applied group. Supplying the bacteria mixture replaced 50% N as the standardized fertilization without reducing the pineapple yield.