Ultra-wideband (UWB) is an indoor positioning technology that has several advantages over current methods of tracking indoor reared broiler chickens, including providing long-term data on movement patterns without the effect of observer presence. More information is needed on the accuracy of this technology under commercial conditions and the effects of wearing an UWB transmitter tag on normal broiler behaviours. Therefore, the main aims of this study were to test the location and distance accuracy of UWB tags, and to determine the effect of wearing backpacks on broiler behaviour and health. In a commercial house, thirty 21-day-old Ross 308 broiler chickens were fitted with an UWB tag backpack. Broilers were then able to move freely among 28 000 con-specifics. In weeks 4, 5 and 6, twenty tagged broilers and twenty untagged broilers were observed for a focal period of 15 min. Tagged broilers were weighed and gait scored on Day 21 and 37. The flock was slaughtered on Day 39 and data for average final weight were taken from slaughter records. The tags displayed a high level of accuracy, with 85 % recording <50 cm from their true location. However, the system consistently overestimated distances. There was no significant difference between the behaviour of tagged and untagged broilers (p>0.05) in weeks 4 or 5. In week 6, tagged broilers spent less time preening than those not wearing a backpack. The average body weight of tagged broilers at Day 37 (2.54 kg) was consistent with average flock final body weights (2.40 kg) and the distribution of gait scores in week 6 was comparable with previous research. In conclusion, the effects of wearing a backpack on broiler health and welfare appeared to be minor, suggesting that data would be representative of normal movement patterns. The UWB system showed a high location accuracy but may be limited in accurately reporting distances travelled.