In this paper, spherical Fe<SUB>3</SUB>O<SUB>4</SUB>/bacterial cellulose (BC) nanocomposites as adsorbents for heavy metal ions were biosynthesized from Gluconacetobacter xylinum by agitation fermentation. A pH controlling embedding method as a new approach was applied to biosynthesize spherical Fe<SUB>3</SUB>O<SUB>4</SUB>/BC nanocomposites. Scanning electron microscopy (SEM) images indicated that the Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles were enwrapped homogeneously in the spherical BC. The spherical Fe<SUB>3</SUB>O<SUB>4</SUB>/BC nanocomposites with 33wt% ferrous loading had 41emu/g of the saturated magnetization (σ<SUB>s</SUB>) and 27Oe of the related coercivity. The adsorption and elution capacities of the spheres for Pb<SUP>2+</SUP>, Mn<SUP>2+</SUP>, and Cr<SUP>3+</SUP> were evaluated. The results indicated that the spherical Fe<SUB>3</SUB>O<SUB>4</SUB>/BC nanocomposites had high adsorption capacities and were recyclable after the elution of heavy metal ions. Compared with conventional preparation procedure for cellulose spheres, spherical Fe<SUB>3</SUB>O<SUB>4</SUB>/BC nanocomposites can be readily prepared without sophisticated steps and have high adsorption and elution capacities.