A Practical Guide to Using This Useful English Structure
What Does "On/Upon Doing" Mean?
The phrase "on doing" or "upon doing" is used to describe something that happens immediately after another action. It’s a formal and concise way to link two events in time.
Both "on" and "upon" are correct and interchangeable, though "on" is more common in modern English.
Structure
On/Upon + verb-ing (gerund)
On arriving home, she called her friend.
Upon hearing the news, he burst into tears.
Common Uses
To express an immediate reaction or consequence.
In formal writing (emails, reports, academic texts).
To replace longer clauses like “as soon as” or “when”.
On opening the door, I saw a surprise party!
( = As soon as I opened the door, I saw a surprise party! )
Tips & Notes
✅ Use "on/upon + -ing" only when the subject of both actions is the same.
❌ Incorrect: On arriving at the station, the train had left. (Who arrived? The train didn’t arrive — you did!)
Correct version:
On arriving at the station, I found the train had left.