A cobalt‐promoted electrochemical 1,2‐diarylation of alkenes with electron‐rich aromatic hydrocarbons via direct dual C−H functionalizations is described, which employs a radical relay strategy to produce polyaryl‐functionalized alkanes. Simply by using graphite rod cathode instead of platinum plate cathode, chemoselectivity of this radical relay strategy is shifted to the dehydrogenative 2+2+2 cycloaddition via 1,2‐diarylation, annulation, and dehydrogenation cascades leading to complex 11,12‐dihydroindolo2,3‐acarbazoles. Mechanistical studies indicate that a key step for the radical relay processes is transformations of the aromatic hydrocarbons to the aryl sp2‐hybridized carbon‐centered radicals via deprotonation of the corresponding aryl radical cation intermediates with bases. Direct C−H functionalizations enable electrochemical diarylation of alkenes with aromatic hydrocarbons using a radical relay strategy toward polyaryl‐functionalized compounds. Chemoselectivity of the strategy relies on choice of both anode and cathode, which is shifted to the dehydogenative 2+2+2 cycloaddition of alkenes with indoles when using graphite rod as the anode and cathode.