This study evaluated the effects of supplementing a rumen-protected choline prototype (RPCP) to transition dairy cows during the dry period and early lactation on performance, metabolism, and immune function, as well as impacts on calf growth and immunity. Holstein cows (n = 72) entering their second or greater lactation were randomly assigned to one of three treatments: 1) control (CTRL; no RPCP), 2) transition (TC; 30 g/d RPCP starting on average 26 d prior to expected parturition through 21 DIM), and 3) full (FC; 30 g/d RPCP starting on average 61 d prior to expected parturition through 21 DIM). Cows were enrolled at dry-off and housed in a freestall pen with Calan gates until 4 wk prepartum, then in tie stalls through 5 wk postpartum, and returned to freestalls through 15 wk of lactation.Blood samples were collected pre- and postpartum to assess metabolic and immune function, including concentrations of NEFA, glucose, BHB, haptoglobin, and cytokines (IL-10, IFN-γ, and TNF-α) following ex vivo LPS stimulation. In addition, liver biopsies were obtained at 7 ± 2 DIM for determination of hepatic triglyceride content as an indicator of liver lipid metabolism. Milk yield and DMI were recorded daily, and weekly samples were collected to assess milk composition, BW, and BCS. Calves remained on-farm through 28 d of life and were evaluated for serum IgG, cytokine production, and ADG. Data were analyzed using repeated-measures ANOVA in PROC MIXED, testing fixed effects of treatment, time, and their interaction; categorical outcomes were analyzed using PROC FREQ. Supplementation of RPCP did not affect milk yield or most components of milk composition; however, transient differences in milk fatty acid profiles for de novo (g/100 g of fatty acids) and preformed (g/100 g of fatty acids and g/d) were observed during early lactation. Cows in both TC and FC treatment groups lost more BW postpartum compared to control cows, despite no differences in DMI, EBAL, or liver triglyceride concentrations. Calf birth weight, growth, and passive transfer of IgG were unaffected by maternal treatment. Overall, varying the duration of supplementation with this particular rumen-protected choline prototype did not result in meaningful improvements in transition cow performance or calf outcomes.