Although bioremediation for oil spill cleanup has received considerable attention in recent years, its satisfactory use in the cleanup of oil spills in the wetland environment is still generally untested. A study of the three most often used bioremediation agents, fertilizer, microbial product and soil oxidant, as a means of enhancing oil biodegradation in coastal mineral and sandy marsh substrates was conducted in controlled greenhouse conditions. Artificially weathered south Louisiana crude oil was applied to sods of marsh (soil and intact vegetation) at the rate of 2 l m−2. Fertilizer application enhanced marsh plant growth, soil microbial populations, and oil biodegradation rate. The live aboveground biomass of Spartina alterniflora with fertilizer application was higher than that without fertilizer. Application of fertilizer significantly increased soil microbial respiration rates, indicating the potential for enhancing oil biodegradation. Bioremediation with fertilizer application significantly reduced the total targeted normal hydrocarbons (TTNH) and total targeted aromatic hydrocarbons (TTAH) remaining in the soil, by 81% and 17%, respectively, compared to those of the oiled controls. TTNH/hopane and TTAH/hopane ratios showed a more consistent reduction, further suggesting an enhancement of oil biodegradation by fertilization. Furthermore, soil type affected oil bioremediation; the extent of fertilizer-enhanced oil biodegradation was greater for sandy (13% TTNH remaining in the treatments with fertilizer compared to the control) than for mineral soils (26% of the control), suggesting that fertilizer application was more effective in enhancing TTNH degradation in the former. Application of a microbial product and a soil oxidant had no positive effects on the variables mentioned above under the present experimental conditions, suggesting that microbial degraders are not limiting biodegradation in this soil. Thus, the high cost of microbial amendments during bioremediation trials may not be warranted in coastal marshes where oil-adapted microbes occur. These results support the conclusion that bioremediation with inorganic nutrient addition has potential for promoting oil spill cleanup in coastal wetlands.