Dystocia has been categorized as a painful event and has been associated with increased risk of cow morbidity, mortality and culling in dairy farms. Administration of NSAID drugs has been proposed to decrease postpartum discomfort. The objectives of this study were to assess the effects of oral administration of acetylsalicylic acid after calving on (1) daily activity patterns and (2) prevalence of diseases, mortality and culling rates in lactating dairy cows. Cows from 3 organic dairy herds were enrolled in the present study. Immediately after parturition, cows were blocked by parity and calving ease [eutocia (EUT); dystocia (DYS)] and were randomly assigned to 2 treatment groups: (1) ASP (n = 278): at approximately 12 h after parturition cows received 4 consecutive treatments with acetylsalicylic acid (100 mg/kg; 2 boluses) 12 h apart; or (2) placebo (PLC; n = 285): at approximately 12 h after parturition cows received 4 consecutive treatments with gelatin capsules (2 capsules) filled with water 12 h apart. Activity monitors were placed on the rear leg of a subset of cows (ASP = 48, PLC = 47) at enrolment, and were removed 7 d later. Overall, there was no difference in lying and standing time between ASP and PLC groups. Cows in the ASP group tended (P = 0.05) to have more steps compared with PLC (ASP = 3514 ± 129 steps/d; PLC = 3162 ± 129 steps/d). Furthermore, cows that experienced DYS spent more time lying (P < 0.05; DYS = 590 ± 17 min/d; EUT = 511 ± 17 min/d), less time standing (P < 0.05; DYS = 850 ± 17 min/d; EUT = 929 ± 17 min/d), and had less steps (P < 0.05; DYS = 3089 ± 126 steps/d; EUT = 3587 ± 133 steps/d) than EUT cows. Additionally, ASP cows that experienced EUT tended (P = 0.06) to spend less time lying and more time standing, and had more (P < 0.05) steps compared with PLC cows that experienced EUT. No difference was found on the incidence of health events, culling and mortality rates between groups. The results of this study suggest that activity patterns of cows that experience DYS are different from cows that experience EUT, and that administration of ASP after calving may increase activity of dairy cows.