Wahaca saw turnover rise in 2018 but in a "challenging market" recorded a slight increase in pre-tax losses.
Parent company Oaxaca reported that turnover had grown to £47.9m in the year to 24 June 2018, from £46.6m the previous year.
Pre-tax losses at the Mexican restaurant brand stood at £4.85m, compared to £4.74m the previous year.
In documents filed with Companies House the group said: "The group operates in a very competitive market which is constantly bringing new concepts and products to the expanding customer base; however we believe that by focusing on looking after and investing in our people the quality and sustainability of our products and customer service that the Wahaca concept offers customers a unique experience that in the long run that gives us a competitive advantage."
The previous year's results had been hit by a norovirus outbreak, which pushed the business into the red for the first time since it began filing full annual accounts in 2010.
It had been forced to close nine of its London sites in October and November 2016 after the outbreak saw 200 staff and 160 diners fall ill.Get The Caterer every week on your smartphone, tablet, or even in good old-fashioned hard copy (or all three!).