on their best behavior
idiom
: exhibiting proper behavior
The children were all on their best behavior at the museum.
Examples of on their best behavior in a Sentence
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Either Silvia and Guojun were not aware that parents under supervision must be on their best behavior—out of love for their children and fear of the state—or this was their best behavior.
—
Ava Kofman, New Yorker, 9 Feb. 2026
Boston Police Commissioner Michael Cox is letting students know about some preparation the department is doing ahead of Super Bowl weekend — and advising them to be on their best behavior.
—Colleen Cronin, Boston Herald, 6 Feb. 2026
At the beginning of a relationship, everyone is usually on their best behavior, which can make this valuable green flag hard to spot early on.
—Baya Voce, CNBC, 27 Nov. 2025
And then there were my bohemian artist parents, a pair of bomb throwers even on their best behavior.
—Daisy Rockwell, Vogue, 27 Nov. 2025
See All Example Sentences for on their best behavior
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Ava Kofman, New Yorker, 9 Feb. 2026
Boston Police Commissioner Michael Cox is letting students know about some preparation the department is doing ahead of Super Bowl weekend — and advising them to be on their best behavior.
—Colleen Cronin, Boston Herald, 6 Feb. 2026
At the beginning of a relationship, everyone is usually on their best behavior, which can make this valuable green flag hard to spot early on.
—Baya Voce, CNBC, 27 Nov. 2025
And then there were my bohemian artist parents, a pair of bomb throwers even on their best behavior.
—Daisy Rockwell, Vogue, 27 Nov. 2025
See All Example Sentences for on their best behavior
Cite this Entry
“On their best behavior.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/on%20their%20best%20behavior. Accessed 14 Feb. 2026.
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