Nitrogen (N) excretion from dairy farming systems is a major environmental challenge. An experiment was conducted to determine the effects of dietary potential digestible fiber (pdF) and crude protein (CP) levels in mid lactating Holstein cows on milk production and content, feeding behavior and nitrogen efficiency. Sixteen primiparous (n = 8) and multiparous (n = 8) cows (BW = kg and DIM = 118 ± 50 d) were allocated to 1 of 4 diets in balanced randomized complete block design in 2 periods (28 d). The diet containing: 1) 19% CP and low pdF, (HPLDF), 2) 17% CP and low pdF, (MPLDF), 3) 15% CP and high pdF, (LPHDF), and 4) 17% CP and high pdF, (MPHDF). The diets were balance for pdF by using different levels of dried alfalfa hay and corn silage in forage proportion of diets. Cows were fed individually and daily dry matter intake was recorded. Daily milk production and bi-weekly milk content were determined. Feeding behavior was recorded in 24 h with exception in milking times. Data were analyzed as repeated measurement with proc MIXED by using SAS software. The diets, periods, times and 2 or 3 ways interactions were constant effects and cows nested in diet and residual errors were random effects. Cows fed the diets with high pdF had greater DMI (17.87, 17.46, 18.44, and 18.60 kg/d, for HPLDF, MPLDF, LPHDF, and MPHDF respectively) and lower (21.8, 17.56, 12.86, and 15.78 for HPLDF, MPLDF, LPHDF, and MPHDF respectively) milk urea nitrogen (P < 0.01) than cows fed low pdF diets. Milk Production and content and blood metabolites were not significantly different among the experimental diets. There was no significant difference among diets in parities and periods. There was significant difference (P < 0.05) among diets in eating activity and cows fed to high pdF diets had greater eating activity (246.85 vs 261.2 min/d for high pdF vs low pdF). Results from this study indicate that increasing cp content in diets with low pdF and also increasing pdF content of diets with mid or low CP content can improve mid lactating Holstein cows’ milk production and efficiency.