The objective of this study was to explore the effects of tail docking and tail biting on pig welfare through an assessment of physiology and behaviour. In experiment 1, piglets were either tail docked using hot cautery iron (CAUT), blunt trauma cutters (BT), or their tails were left intact (CON). Blood samples were taken from pigs at 3 and 7 weeks of age to measure C-reactive protein (CRP). Tail-biting lesions were scored at 3, 5, and 7 weeks of age. Behaviour was recorded for 72 h when tail biting was observed in 7-week old pigs. Tail-biting lesion scores were similar among treatments at 3 and 5 weeks of age, however at 7 weeks lesion scores were greater among CON compared with CAUT and BT pigs. Bodyweights were lower among CON compared with CAUT or BT pigs and CRP was elevated among CON compared with CAUT and BT pigs at 7 weeks of age. In experiment 2, piglets were tail docked at a length of 2 cm (Short) or 5 cm (Long). Tail-biting lesions were scored every 2 weeks until the end of finishing. Tail-biting lesion scores were greater among Long compared with Short pigs. Compromised welfare of tail-bitten pigs was indicated by severity of lesion, level of CRP, and reduced pig bodyweights. More research is needed into understanding the causative factors behind tail biting in pigs, so that preventative measures can be adopted on farms to prevent this behaviour.