Bactericera cockerelli Šulc (Hemiptera: Psylloidea: Triozidae), also known as the potato psyllid, is a pest of pepper and potato crops in northern Mexico. Growers control it by applying insecticides, without knowing the tolerance or resistance levels to these pesticides. The goal of this study was to determine the resistance ratios of several populations of B. cockerelli from regions of northern Mexico. Three populations of B. cockerelli were collected from sample sites at Coahuila—Nuevo León, San Luis Potosí, and Aguascalientes and compared with a laboratory susceptible line. Results indicated that populations from Aguascalientes had resistance ratios of 1.69-, 1.26-, and 1.00-fold for the insecticides abamectin, endosulfan, and imidacloprid, respectively. The corresponding ratios were 10.72-, 2.52-, and 3.75-fold for the San Luis Potosí population and 2.57-, 3.75-, and 4.22-fold for the Coahuila—Nuevo León population. We conclude that the B. cockerelli population of only San Luis Potosí was resistant to abamectin, but that the other 2 populations were susceptible to it. All 3 populations were fairly susceptible to endosulfan and imidacloprid.