The aim of this study was to identify which age and method of castration causes less acute pain and distress in beef calves. One hundred five Angus bull calves were blocked by age and body weight, and randomly assigned to 1 of 3 treatments: control (C; n = 12); band castration (B; n = 12); and surgical castration (S; n = 12); at 1 wk, 2 and 4 mo of age. Physiological and behavioral parameters were collected before, during and after castration to assess acute pain. Physiological measures included blood count, salivary cortisol, haptoglobin, substance P and infrared thermography. Behavioral measures consisted of visual analog score, stride length, hobo data loggers and behavioral scoring of walking, standing, lying, tail flick, foot stamping and head turning. Overall, no physiological or behavioral parameters differed significantly for calves castrated at 1 wk of age. Salivary cortisol tended (P = 0.07) to differ at 1 wk of age when S calves had greater concentrations than B calves. Conversely, both physiological and behavioral indicators of pain/distress were clearly observed when calves were castrated at 2 and 4 mo of age regardless of the method used. A time × treatment interaction (P < 0.0001) was observed for salivary cortisol in 4 mo old calves, with B and S calves having greater concentrations than C calves 60 min after castration, while B had greater concentrations than S and C calves 120 min after castration. Based on behavioral data, S calves at 2 and 4 mo of age, stood (P < 0.0001) and walked (P = 0.04) more but lie down and ate less (P = 0.01; P = 0.002) compared with B and C only at 2 mo of age. At 4 mo of age, S calves tail flicked more (P = 0.0006) and had shorter stride length (P = 0.036) than B and C calves. The indicators of acute pain/discomfort assessed in this study suggest that the most welfare-friendly age and method of castration is band castration at 1 wk of age.