The welfare impact of birth on newborn calves has rarely been studied. Dystocia in particular may have significant welfare costs for calves. While analgesia is sometimes provided to calves born to difficult parturition by veterinary surgeons in practice, it is not known if this is actually beneficial. On a commercial dairy farm, we examined the behavioural time budget of 39 Holstein heifer calves born with the aid of farmer assistance and 36 calves born without assistance; half of each group were randomly allocated to receive either a single dose of the non-steroidal anti-inflammatory drug ketoprofen or a saline placebo in a two by two factorial design. The calves were group housed and their behaviour was recorded for 48 hours postpartum and analysed using instantaneous focal sampling (every 5 minutes in alternate hours). Regardless of analgesic treatment, calves born with assistance showed behaviours consistent with experiencing a less positive welfare state (lying with their head down and in lateral recumbency, and less time playing than unassisted calves). Behavioural differences between calves treated with ketoprofen and calves treated with saline (in particular increased play) suggest that the birth experience may be painful for all calves, even if no assistance is required. Our findings suggest that a single dose of ketoprofen in the immediate postpartum period may improve calf welfare regardless of assistance status and has the potential to contribute to significant welfare gains in dairy calves.