Removal of Fe(II) and Mn(II) ions from aqueous solution by fungal biosorbent Aspergillus sp. TU-GM14immobilized on Detarium microcarpum matrix was investigated in this study. Effects of biosorption parameters pH, biosorbent concentration, bead size and equilibrium time on Fe(II) and Mn(II) ions sorption were also determined. Equilibrium was attained within in 3 hours while optimum Fe(II) and Mn(II) ions removal was observed at pH 6, 8 mm bead size, 2 g l-1 spore load respectively. Adsorption capacity was described using Langmuir, Freundlich and BET isotherm models. The experimental data fitted best to the Freundlich model (R2 0.992 and 0.996 for Mn(II) and Fe(II) respectively). Favourable surface sorption process was described by Langmuir isotherm for both metals (Qmax 34 and 14 mg g-1 for Mn(II) and Fe(II) ions) while the BET isotherm constant, B, described high metals sorption beyond the biosorbent surface in a multi-layer sorption process (4.8 and 9.0 for Mn(II) and Fe(II) respectively). Results of the study showed that Aspergillus sp. TU-GM14 biosorbent can remove large quantities of Fe(II) and Mn(II) ions from solution in both surface and multi-layer sorption process with Detarium microcarpum acting as a cheap immobilization matrix.