Two experiments were carried out to evaluate the efficiency of weed con trol by herbicides, applied singly or in combination with boron (B), and the response of sunflower (Helianthus annuus L.) to fertilization with this micro nutrient. Herbicides were applied to the plots whose sub-plots involved the presence or absence of 2 kg ha-1 of B, from two different sources (H3BO3 boric acid and Na2B8O13 ·4H2O– sodium borate) mixed with the herbicides. The combinations of the herbicides and boron, preferentially from the source H3BO3, efficiently controlled the following weeds: wild poinsettia (Euphorbia heterophylla), hairy beggarsticks (Bidens subalternans), and alexandergrass (Brachiaria plantaginea). The application of B in association with herbicides increased the content of this micronutrient in the soil and consequently in sun flower leaves. The combined application of herbicides and boric acid appears to be perfectly suitable for controlling weeds while increasing the mineral nutrition of sunflower.