Ozonation for micropollutant removal from wastewater treatment plant effluent is energy and cost-intensive because of competition between background organic matter and micropollutants. This study aims to elucidate the interference of different organic matter fractions during the ozonation of micropollutants. Wastewater treatment plant effluent was fractionated using membranes and XAD-8 resin. All membrane and resin fractions were spiked with 18 micropollutants (2 µg/L) and ozonated with 0.25, 0.5 and 1 g O3/g TOC. Results show that these fractions differ in their interference with the ozonation of micropollutants. Interference was lower in the smallest size fraction (<1 kDa) than in all other fractions for micropollutants with low and medium ozone reactivity. The hydrophobic neutrals and hydrophilics resin factions showed a high interference for ozonation of micropollutants with medium and high ozone reactivity, respectively. The four parameters that were analyzed (specific UV absorbance at 254 nm, fluorescence, chemical oxygen demand and nitrite) could not elucidate the differences in micropollutant removal. Still, we conclude that understanding the type of organic matter present in the matrix, is essential to optimize micropollutant ozonation and other tertiary micropollutant removal treatments.