Abstract: The objectives of this study were to evaluate the influences of milk yield and fertility traits in the first lactation on the Length of Productive Life (LPL) of Holstein dairy cows in Iran. Records of Holstein-Friesian cows born from 1993-2006 on 7 large-scale farms were analyzed. The length of productive life was defined as the number of days from first calving to the date of death or culling on the farm. The dependent variable analyzed was LPL. The model included herd, sire, milk yield and fertility traits in the first lactation and also culling year and culling category. Data were analyzed using General Linear Models using the statistical software package JMP. Length of productive life averaged 3.52�0.03 year. The result showed that sire, herd and culling year impacted LPL (p<0.01). Length of productive life was impacted by 305-day adjusted milk yield (p<0.001) and the LPL was decreased in high producing cows compare with the average cows. The LPL was higher in the cows with eutocia compare with dystocia and stillbirth groups in the first calving (p<0.01). Age at first calving had significant effect on LPL (p = 0.035). The LPL was impacted by the culling groups (p<0.001). LPL for cows which culled due to sold for dairy purposes was the lowest and for reproductive problems was the greatest compare with the other categories. The result of this study demonstrated that in addition to sire and herd effects some other variables had significant impact on LPL.