To quantify the efficacy of effective weed control methods and spacing of groundnut on soil microbiological properties, a field experiment was conducted between 2009 and 2010 at the Teaching and Research Farm of the University of Agriculture, Abeokuta, a sub-humid region of southwestern Nigeria. Treatments were five levels of weed control (codal gold 1.6 kg a.i/ha, codal gold 1.6 kg a.i/ha + hoe weeding, codal gold 2.4 kg a.i/ha, hoe weeding and a control (weedy check); two levels of spacing (15 cm and 25 cm) and eight levels of weeding intervals on soil microbial biomass, nodulation, the biomass of root and shoot as well as yield of groundnut in a split-plot design fitted into a randomized complete block design. The results indicated that both levels of spacing have no significant effect on the soil microbiological parameters, groundnut biomass production, nodulation and yield. So, the levels of weed control have no significant effect on groundnut biomass production and nodulation but showed a significant effect on microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), total fungal count, pod count and pod weight of groundnut with plots kept weedy throughout the experiment at 25 cm intra row spacing having 34 % MBC more than plots kept weed free throughout the experiment at the same spacing.