Abstract The expanding knowledge of the health impacts of the metabolic activities of the gut microbiota reinforces the current interest in engineered probiotics. Tryptophan metabolites, in particular indole lactic acid (ILA), are attractive candidates as potential therapeutic agents. ILA is a promising compound with multiple beneficial effects, including amelioration colitis in rodent models of necrotizing enterocolitis, as well as improved infant immune system maturation. In this work, we engineered and characterized in vitro and in vivo an Escherichia coli Nissle 1917 strain that produces ILA. The 2-step metabolic pathway comprises aminotransferases native of E. coli and a dehydrogenase introduced from Bifidobacterium longum subspecies infantis. Our results show a robust engineered probiotic that produces 73.4 ± 47.2 nmol and 149 ± 123.6 nmol of ILA per gram of fecal and cecal matter, respectively, three days after colonization in a mouse model. In addition, hereby is reported an engineered-probiotic-related increase of ILA in the systemic circulation of the treated mice. This strain serves as proof of concept for the transfer of capacity to produce ILA in vivo and as ILA emerges as a potent microbial metabolite against gastrointestinal inflammation, further development of this strain offers efficient options for ILA-focused therapeutic interventions in situ.