The para‐selective C−H alkylation of aniline derivatives furnished with a pyrimidine auxiliary is herein reported. This reaction is proposed to take place via an N−H‐activated cyclometalate formed in situ. Experimental and DFT mechanistic studies elucidate a dual role of the ruthenium catalyst. Here the ruthenium catalyst can undergo cyclometalation by N−H metalation (as opposed to C−H metalation in meta‐selective processes) and form a redox active ruthenium species, to enable site‐selective radical addition at the para position. Para‐normal activity: The para‐selective C−H alkylation of aniline derivatives is reported. The methodology is proposed to proceed by a dual role ruthenium process: cycloruthenation at N−H and redox radical generation. This strategy leads to para‐selective alkylations using pyrimidine and quinazoline auxiliaries.