Nitrification is a crucial process in sediment nitrogen cycling. We compared two ¹⁵N tracer-based nitrification measurement techniques (isotope pairing technique (IPT) combined with ¹⁵N nitrate pool dilution and ¹⁵N ammonium oxidation) and three different ¹⁵N analyses from bottom water nitrate (ammonia diffusion, denitrifier and SPINMAS) in a sediment mesocosm. The ¹⁵N nitrate pool dilution technique combined with IPT can be used to quantify the in situ nitrification, but the minimum detection limit for the total nitrification is higher than that in the ¹⁵N ammonium oxidation technique. The ¹⁵N ammonium oxidation technique, however, is not applicable for sediments that have high ammonium content. If nitrate concentration and the amount of ¹⁵N label in the sample are low, the ¹⁵N nitrate analysis should be done with the denitrifier method. In higher ¹⁵N concentrations, the less sensitive SPINMAS method can also be applied. The ammonia diffusion method is not suitable for bottom water ¹⁵N nitrate analyses.