Sulfonylurea herbicides mixtures with phenoxy herbicides can lead to effective control of broadleaved weeds. Pot experiments were conducted to study the effect of foramsulfuron and nicosulfuron mixtures with 2,4-D plus MCPA on redroot pigweed and common lambsquarters in 2010 at the greenhouse of Agricultural Faculty of Ferdowsi University of Mashhad, Iran. Experiments were performed as a completely randomized design with four replications. Treatments consist of several doses of sulfonylurea herbicides, which applied alone or in combination with 2,4-D + MCPA at different ratios at two- to four- true leaf stage. Also, to study the single-cross 704 corn (Zea mays L.) injury by applying herbicides alone or in mixture with different ratios, an experiment was conducted in 2011 at the farm of the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. Based on greenhouse results, effective dose of 2,4-D + MCPA did not decrease in the 87.5:12.5 mixture ratio of 2,4-D + MCPA with foramsulfuron or 75:25 and 50:50 mixture ratios of 2,4-D + MCPA with nicosulfuron on redroot pigweed. This may be caused by interference between herbicides for absorption and translocation. While, interference was observed at equal’s or higher mixture ratios of foramsulfuron in mixture with 2,4-D + MCPA on common lambsquarters. Weed species, metabolism rate of herbicide and cuticle structure can be important in higher doses’ application of herbicides in mixture and interference between two herbicides. Besides, weed growth stage, more entrance directions and transition of elaborated sap can be effective in translocation of herbicides in an effective dose to the site of action and less interference between herbicides. Sulfonylurea herbicides mixtures with 2,4-D + MCPA did not cause much injury on corn plants based on field study.