The objective of this study was to assess the effect of ketosis status on behavioral activity in transition dairy cows. A behavioral activity index (BAI) was computed for every animal taking into account the number of steps (no./d), standing time (min/d), lying time (min/d), and lying bout (LB, no./d). A total of 387 Holstein dairy cows (110 primiparous and 277 multiparous) in 3 commercial dairy herds were enrolled at 7 d before calving until 14 d post-calving. Weekly, a cohort of 10 to 15 cows was enrolled at each farm and electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) were fitted to the hind leg of individual cows to assess their behavioral activity. Postpartum cows were screened for ketosis (KET) at 7 and 14 DIM by measuring β-hydroxybutyrate in serum samples (Nova Vet Ketone Test Strips). A case of KET was recorded when lactating cows had serum concentration of β-hydroxybutyrate ≥1.2 mmol/L. Cases of metritis, retained placenta, lameness, milk fever, or mastitis during the study period were recorded and lactating cows were allocated into 1 of 4 groups: 1) non-disease (ND, n = 248; cows without KET and any other health conditions), 2) cows with only KET (n = 64), 2) sick cows experiencing ≥ 1 health conditions, but without KET (SICK, n = 59), or cows with KET plus at least 1 health condition (KET+H, n = 17). The BAI was computed for the first 7 DIM to assess differences among cow health groups. Data were analyzed using MIXED procedure of SAS. Primiparous cows (P < 0.05) had greater BAI compared with multiparous cows and as cows mature, they become less active early in lactation regardless of health status. Cows experiencing KET, SICK and KET+H had reduced BAI (93.1, 56.6 and 95.5, respectively) compared with ND cows (P < 0.05). These results suggest that monitoring a combination of behavioral metrics, such as the BAI, could contribute to consistently identifying cows experiencing KET with another health conditions in transition cows. Health status early in lactation is significantly associated with removal of lactating cows from the milking herd; thus affecting the bottom line of dairy operations.