It is not illegal to record phone calls in Missouri, under certain circumstances.
The Missouri law regarding tape recording phone calls can be overwhelming. It is not illegal to record phone calls secretly, as long as one party to the conversation knows it is being recorded. This means that Missouri and Federal eavesdropping statutes specifically do not apply as long as one party to the conversations knows it is being recorded. Approximately twelve states, including Illinois, prohibit tape-recording any conversations without the other person’s knowledge or a search warrant.
Thus, in Missouri, if a person tapped his or her phone to record conversations with another party, it would be legal. The remains true only so long as you were the only person who used that phone. Or if at least one other party to all conversations knew it was being recorded. If a person secretly tape records phone conversations between two individuals who are unaware that the conversations are being recorded, that person would be in violation of eavesdropping laws. The question of the legality of taping phone conversations often comes about in the context of divorce cases, orders of protections, and drug cases.