The objectives of this study were to investigate colostrum quality in Isfahan commercial dairy farms and to determine the effects of season of calving and parity of dam on colostral composition. Colostrum samples from Holstein cows were collected from 11 dairy farms between January 2011 and November 2012. Colostrum samples from 365 cows were analyzed for concentrations of IgG, IgM, total solid, fat, protein, lactose, Ca and P. The concentration of IgG and IgM were determined by ELISA (kit E10-118 and 101, Bethyl Laboratories, Montgomery, TX). Data were analyzed by using SAS statistical software and the GLM procedure. The IgG and IgM contents were 35.83 and 5.82 mg/ml, respectively. Percentage of total solid, fat, protein and lactose were 27.24, 4.75, 18.5 and 2, respectively. Concentrations of Ca and P were 2691.73 and 1937.32 mg/kg, respectively. Volume of first milking colostrums did not have any significant effect on colostral composition. Season of calving significantly influenced the Ig concentration. Colostral IgG and IgM concentrations were significantly higher in the winter. The content of IgG in the fall and spring did not significantly differ and was in the lowest level. The concentration of IgG was intermediate in the summer. Season of calving did have a significant effect on concentrations of fat. The lowest value of fat content was in the spring and fall. In addition, the amount of Ca and P was influence by season and had the highest value for both concentrations of Ca and P in the summer season. Concentrations of IgG and IgM colostral did not changed significantly by parity of dam. However there were an upward tendency for Ig concentration with increasing parity, cows in their forth parity did have significantly lower IgG and IgM concentrations than others. Decreasing trend for concentration of Ca and P found with increasing parity. The amount of Ca and P almost were constant after third parity. The management practices among farms seem to be theoretically acceptable but a lot needs to do practical whatever exist in theatrical words. Furthermore, what is worth noticing fact is that consider the colostrum of 1st parity more. In a word, taking into account of all these factors, we may reach the conclusion that season of calving is more effective than parity of dam on Ig concentration. Regard to that only 18.6% of our samples had more than 50 mg/ml IgG highly recommend that Isfahan industrial dairy farms to expand their endeavors in order to consider quality of colostrum by seasonal effect more than past to guaranty the future and health of replacement heifers and farms. Key Words: Colostrum, parity, season of calving, volume of colostrum