The teenage climate activist made the tongue in cheek vow after being filmed chanting "you can shove your climate crisis up your a***" and telling crowds "no more exploitation, no more whatever the f*** they're doing inside there".
On Wednesday, the 18-year-old tweeted: "I am pleased to announce that I’ve decided to go net zero on swear words and bad language. In the event that I should say something inappropriate I pledge to compensate that by saying something nice."
Weighing in on the joke, one Twitter user asked if Ms Thunberg would "commit to reaching net-zero bad language by 2050".
Ms Thunberg responded: "No, by 2052 with a 39.78% reduction by 2034".
The Swedish activist is one of the summit's fiercest critics - she has long argued that change won't come from the conference without public pressure.
Greta comes to Glasgow: The most famous climate protestor in the world leads a demonstration across the river from COP26
In the first three days of the conference, over 100 world leaders pledged to end deforestation by 2030, while over 80 countries vowed to cut their methane emissions by the end of the decade.“Inside COP they are just politicians and people in power pretending to take our future seriously," Ms Thunberg said at a protest across the river from the summit on Monday. "Pretending to take the present seriously of the people who are being affected already today by the climate crisis.
“We say no more blah blah blah, no more exploitation of people and nature and the planet".