Tylenol (acetaminophen) typically starts working within 20 to 45 minutes after taking it orally. Effervescent or dissolvable forms may act faster, often within about 20 minutes, while regular tablets usually take around 30 to 45 minutes to begin pain relief. Taking Tylenol on an empty stomach can help it work slightly faster. The effects usually last about 4 to 6 hours depending on the formulation and dosage.