Objective This study was conducted to evaluate the interactive effects of dietary digestible tryptophan (dTry) and soy oligosaccharides (SO) on growth performance, caecal skatole level, and microflora of broiler chickens aged from 14 to 42 days. Methods Three hundred and sixty broiler chicks were allocated equally to 36 cages at 14-day-of-age according to body weight and gender. Using a 3×2 factorial arrangement, 3 dietary dTry levels (0.18%, 0.23%, and 0.28%) supplemented with 0 or 3.5 g/kg of SO were used to create 6 diets (treatments). Each diet was fed to six replicates of 10 birds (60 birds/treatment), growth performance was measured. Caecal content samples were collected at 42 days of age. Results Results showed that significantly different dTry level×SO interactions were found for average daily gain (ADG), caecal levels of indole, propionic acid, and butyric acid, and microbial Shannon index (p