Under both Minnesota law,  and federal law,  as long as you yourself are a party to the conversation, it is lawful for you to record that conversation, even secretly. Furthermore, such recordings happen often enough in family practice that you are wise to assume that any telephone conversation with your spouse is in fact being recorded, and to temper your speech accordingly — i.e., no anger, name-calling, or spiteful speech of any kind. Such recordings of your spouse may be used in evidence, provided they’re relevant. However, they shouldn’t be used unless they are very compelling and necessary evidence of the point you’re trying to prove, because otherwise their usefulness is outweighed by the tendency of such recordings to make you look obsessive. A trickier question is whether you may record the other parent's conversations with the children. Under the doctrine of "vicarious consent," as long as a parent or guardian has "a good faith, objectively reasonable belief that the interception of telephone conversations is necessary for the best interests of the children," then he may consent to the interception (i.e. listening in or recording the call) on behalf of the children.  However, this can be risky, because if there is any dispute about whether your vicarious consent was in good faith or objectively reasonable, you may still end up having to defend against possible criminal charges or a civil lawsuit. The Wagner case I have cited, for example, was a civil lawsuit by a one parent against the other parent who had recorded telephone calls between the children and herself. The Court allowed that lawsuit to proceed because there was a genuine issue of material fact as to the motivations of the parent who had made the recordings. I don't recommend recording any such phone calls without first consulting a lawyer. Endnotes:  Minnesota Statute section 626A.02, Subdivision 2(d).  18 U.S.C.A. section 2511(2)(d).  Wagner v. Wagner, 64 F.Supp.2nd 895 (D.Minn. 1999).