Externally and intentionally initiated inhibitory processes, which are fundamental for human action control, can be unconsciously launched. However, the neural oscillatory mechanisms underlying unconscious priming of externally and intentionally generated inhibition remain unclear. This study aimed to explore this issue by extracting oscillatory power dynamics from electroencephalographic data with participants performing an unconscious version of the Go/No-Go/Choose task involving subliminally presented primes. The participants presented prolonged response times upon being instructed or intentionally deciding to commit a "Go" response following a No-Go prime compared with those following a Go prime. This indicates that unconscious inhibitory processes can be externally and intentionally initiated. Time-frequency analysis indicated increased theta band oscillatory power on the forced Go response following a No-Go prime compared with that following a Go prime. Contrastingly, there was pronounced alpha/low-beta band oscillatory power on the free-choice Go response following a No-Go prime compared with that following a Go prime. Moreover, there was a positive correlation of theta and alpha/low-beta band oscillations with human behavior performance related to the two distinct unconscious inhibitory processes. Our findings delineate dissociable neural oscillatory mechanisms underlying the unconscious priming of externally and intentionally initiated inhibition. Moreover, they might provide complementary neural oscillatory evidence supporting the discrepancy between instructed and voluntary human action control.