We report the emergence of the novel MEK1 V211D gatekeeper mutation in a patient with BRAF K601E colon cancer treated with the allosteric MEK inhibitor binimetinib and the anti-epidermal growth factor receptor (EGFR) antibody panitumumab. The MEK1 V211D mutation concurrently occurs in the same cell with BRAF K601E and leads to RAF-independent activity but remains regulated by RAF. The V211D mutation causes resistance to binimetinib by both increasing the catalytic activity of MEK1 and reducing its affinity for the drug. Moreover, the mutant exhibits reduced sensitivity to all the allosteric MEK inhibitors tested. Thus this mutation serves as a general resistance mutation for current MEK inhibitors; however, it is sensitive to a newly reported ATP-competitive MEK inhibitor, which therefore could be used to overcome drug resistance.