MCCarthy sparked the online confrontation when she went public with a story she'd overheard about an alleged police raid on the Hairspray star's home in New York on Wednesday night (01May13).
The former Playboy pin-up tweeted, "Police are at Amanda Bynes' house. I hope they get her help. Enough of this circus. She needs help."
But she confessed that she wasn't completely convinced her information was correct, adding, "It came from a publicist but if no one can back it up it could be wrong."
And it seems she was ill-advised to tweet the 'breaking news' as Bynes, who has become a tabloid target in recent months thanks to a series of odd tweets and bizarre behaviour on the streets of New York, fired back: "@JennyMCCarthy you're ugly! Police weren't at my house old lady! Shut the f**k up! I need help? What are u talking about? Aren't u 50 years old? I'm 27, u look 80 compared to me! Why are you talking about me?"
MCCarthy later apologised for spreading the rumour, tweeting, "@AmandaBynes sorry girl. Looking out for ya."
And it appears the two have now made nice - Bynes later added, "@JennyMCCarthy thanks! I'm sorry I offended you! You're beautiful! I was lying! I'll delete our tweets!"