Calf stress at weaning and after transfer to group pens is a concern in dairy farms. Favoring natural behaviors, such as grooming, may help to reduce this challenge. Our objective was to evaluate the effect of a mechanical brush on the performance and behavior of recently weaned calves. A paired comparison design with 2 treatment groups (control [CON, n = 81], treatment [TRT, n = 81]) was performed. Organic Holstein heifer calves (94 ± 7 d old) were each monitored for 3 wk. Four cohorts were enrolled sequentially considering one CON and one TRT group (1 brush/pen, n = 19–20 calves/pen). At enrolment, each calf was weighed and subject to a health evaluation. A 3-D accelerometer sensor was attached to the left ear. Continuous and excluding measurements (min/h) were generated for the following behaviors: Not-active, active, highly active, eating, and ruminating. Calf were weighted at the last day of the study. Data were summarized as daily averages (min/h). In addition, total monitoring time was divided in 4 periods of 5 d and analyzed as hourly averages (min). Data were examined using repeated measures analyses ANOVA, considering values by day or hour as the repeated measure. No difference was found in average daily weight gain between treatment groups. Significant differences were found for the interaction time and treatment group, indicating greater values for CON calves on the time spent not-active (22.8 ± 0.82 vs. 21.7 ± 0.82 min/h; P = 0.014) and lower values for the time eating (6.43 ± 0.40 vs 7.01 ± 0.40 min/h; P = 0.01) during the 20 d in study. Hourly not-active time was greater for CON pens for Period 1 (18.3 ± 0.78 vs 17.9 ± 0.78 min/h; P < 0.001), Period 2 (24.7 ± 1.08 vs 22.8 ± 1.08 min/h; P = 0.01). Similarly, differences in favor of TRT group were found for time with high activity in Period 2 (10.3 ± 0.57 vs 10.0 ± 0.57 min/h; P < 0.001), Period 3 (9.7 ± 0.58 vs 9.1 ± 0.58 min/h; P = 0.049), and Period 4 (9.9 ± 0.58 vs 9.6 ± 0.61 min/h; P = 0.02). Differences in daily eating time were found for Period 1 in favor of CTR (8.3 ± 0.51 vs 8.0 ± 0.51; P < 0.001 min/h) and Period 2 in favor of TRT group (6.44 ± 0.54 vs 5.48 ± 0.54 min/h; P = 0.003). We conclude that the use of a mechanical brush throughout the days of group housing reduced inactive time, while increasing eating time.