The antimicrobial triclosan was analyzed in unfiltered samples from influent, effluent, and receiving stream and before and after a pilot-scale constructed wetland at a North Texas municipal wastewater treatment plant. Triclosan concentrations were reduced by 97 to 99% by the activated sludge treatment plant. Effluent concentrations were further reduced by passage through the constructed wetland, but receiving stream concentrations were not statistically significantly different from effluent concentrations. Effluent concentrations of triclosan were seasonal with highest concentrations occurring during the summer months. The effluent-dominated receiving stream maximum concentrations during summer months were below reported algal no-observed-effect concentrations based on biomass and growth rate but exceeded concentrations reported to cause shifts in algal community structure.