Simple SummaryGrowth performance and feed efficiency of growing and fattening pigs is closely linked with gastrointestinal health. Τhe ban of using antibiotics as growth factors in the EU has directed research efforts towards alternative dietary and management tools to maintain pig performance. Clay minerals, and especially attapulgite, are among those materials with a variety of properties that can serve this purpose. The current study investigated the effects of the dietary supplementation of attapulgite on the performance of pigs from weaning to slaughter in three commercial pig farms in Greece. The results suggest that attapulgite dietary supplementation can improve pig growth and feed efficiency subject to continuous supplementation from the post-weaning period.The objective of the present study was to investigate the effect of dietary supplementation of attapulgite on the performance of fattening pigs from weaning to slaughter under field conditions in three commercial farrow to finish herds. In total 1890 pigs were used for six months: 720 pigs in Farms A and B, respectively and 450 pigs in Farm C. The pigs were equally allocated in three dietary treatments: CON, standard diet in each growing phase; ATT, standard diet that was supplemented with attapulgite at 7 kg/tn of feed; and ATT+, standard diet that was supplemented with 8 kg/tn of feed with a compound product based on attapulgite. Pigs that were fed diets that were supplemented with attapulgite (ATT and ATT+) had significantly higher (p < 0.05) average daily feed intake (ADFI) and a better feed conversion ratio (FCR), compared to the control (CON). In conclusion, attapulgite supplementation in the diet of pigs from weaning to slaughter can improve their performance in commercial farms.