► Anammox is a new process for monosodium glutamate (MSG) wastewater nitrogen removal. ► Conventional activated sludge can be the seeding source for MSG wastewater treatment. ► Sludge from the MSG wastewater treatment plant was the best seeding sludge. Three activated sludges from a landfill leachate treatment plant (S1), a municipal sewage treatment plant (S2) and a monosodium glutamate (MSG) wastewater treatment plant (S3) were used as inocula to enrich anaerobic ammonium oxidation (anammox) bacteria for the startup of MSG industrial wastewater treatment system. After 360 days of cultivation using MSG wastewater, obvious anammox activity was observed in all three cultures. The maximum specific anammox activities of cultures S1, S2 and S3 were 0.11 kg N kg −1 VSS day −1, 0.09 kg N kg −1 VSS day −1 and 0.16 kg N kg −1 VSS day −1, respectively. Brownish-red anammox granules having diameters in the range of 0.2–1.0 mm were visible in cultures S1 and S2, and large red granules having diameters in the range of 0.5–2.5 mm were formed in culture S3 after 420 days of cultivation. Phylogenetic analysis of 16S rRNA genes showed that Kuenenia organisms were the dominant anammox species in all three cultures. The copy numbers of 16S rRNA genes of anammox bacteria in cultures S1, S2 and S3 were 6.8 × 10 7 copies mL −1, 9.4 × 10 7 copies mL −1 and 7.5 × 10 8 copies mL −1, respectively. The results of this study demonstrated that anammox cultivation from conventional activated sludges was highly possible using MSG wastewater. Thus the anammox process has possibility of applying to the nitrogen removal from MSG wastewater.