Abstract How tropical cyclone (TC) frequency may change following volcanic eruptions remains debated, owing to limited contemporary eruption samples. Using last‐millennium multi‐member simulations with CESM, we show that post‐eruption TC genesis potential over the western North Pacific consistently decreases during the storm season following extremely strong tropical volcanic eruption (>∼50 Tg sulfate aerosol). In contrast, for moderate‐to‐very‐strong eruption (∼9–50 Tg), the sign of post‐eruption genesis potential change varies greatly across individual ensemble members, suggesting that internal climate variability plays a dominant role relative to eruption magnitude. This spread in the sign of genesis potential change is attributed to tropical Pacific temperature conditions preceding the eruptions, with a negative (positive) phase of the El Niño–Southern Oscillation in the pre‐eruption winter associated with an increase (decrease) in post‐eruption genesis potential. Our results highlight the important role of initial oceanic conditions in regulating post‐eruption TC genesis potential for a given eruption event.