The Australian 2019–2020 wildfires impacted the subtropical rainforest with a variety of burn severities, making them vulnerable to another burn. Rainforest post-fire regenerated vegetation could be highly flammable, containing fire-promoting species such as Lantana camara and fire-suppressing species such as Phytolacca octandra. This study investigated whether early post-fire regeneration may make rainforests more flammable and if this varies with fire severity. This study sampled three national parks where rainforest burnt in 2019–2020 across different fire severities to test if there were consistent patterns in post-fire regeneration flammability. We found that flammable species increased in the regions where fire severity was higher.