Owing to the increased occurrence of antimicrobial resistances, alternatives to antibiotics to treat post-weaning diarrhoea (PWD), especially in case of prophylactic use, is crucial. This study aimed to study whether a standard diet (SD) supplemented with 2% chestnut extract (CE; Silvafeed Nutri P/ENC, Silvateam, Italy) could affect the severity of PWD, organic matter digestibility and intestinal bacterial population of piglets infected or not with enterotoxigenic E. coli (ETEC) F4. At weaning, 48 piglets were allocated in a 2 x 2 factorial design balanced for weaning body weight and litter. Three pigs were housed per pen where they had ad libitum access to either the SD or CE diet. In each of the 2 dietary groups, 4 d after weaning, 12 piglets were orally infected (INF) with 5 ml of an ETEC (F4ac, LT+, STb+) suspension (108 CFU/ml), whereas the remaining 12 pigs received 5 ml PBS (NINF). Faecal score and faecal dry matter were monitored daily. Piglets were sacrificed 3, 6 or 7 d post-infection and jejunum and colon contents were collected to determine bacterial population and organic matter digestibility. The ETEC infection resulted in greater faecal score and lower faecal dry matter (P< 0.05 for each) but had no (P>0.10) effects on feed intake per pen, average daily weight gain, organic matter digestibility nor bacterial population in the jejunum. Feed intake per pen and organic matter digestibility were similar (P>0.10) between SD and CE groups. However, piglets fed the CE diet tended (P=0.08) to be 43 g heavier than those fed the SD diet. Compared with the SD diet, supplementation with CE reduced faecal score and increased faecal dry matter (P< 0.05 for each). Preliminary results on bacteria quantification indicate a lower (P≤0.09) relative quantity of Clostridium cluster IV and Lactobacillus in the jejunum of CE compared with SD piglets. The results of this study suggest that regardless of ETEC infection, chestnut extract reduces faecal score and modifies bacterial population in the jejunum without altering organic matter digestibility.