Synonyms for Be on best behavior:

• v.

  •act reasonably, properly (verb)
  • behave.
  •behave (verb)
  • deport oneself,
  • conduct oneself properly,
  • mind one's manners,
  • play fair,
  • comport oneself,
  • discipline oneself,
  • mind one's p's and q's,
  • be nice,
  • direct,
  • act correctly,
  • watch one's step,
  • live up to,
  • be civil,
  • keep the peace,
  • toe the mark,
  • manage oneself,
  • observe the law,
  • be good,
  • shape up,
  • keep one's nose clean,
  • observe golden rule,
  • demean oneself,
  • act one's age,
  • be orderly,
  • act with decorum,
  • manage,
  • control.

• Other synonyms:

  •behave
  • watching one's step,
  • mind p's and q's,
  • minding p's and q's.

Antonyms for Be on best behavior:

• v.

  • behave
    act up, misbehave.