The best time to start mediation is whenever you and your spouse each feel ready to start mediation. This can come at any point during the divorce process. You can start going to mediation before you and your spouse have finalized your decision to separate. Or you can pursue mediation after filing a Complaint for Divorce. The key is that both spouses needed to be ready. Many former spouses mediate post-divorce issues after the divorce is finalized.
In general, spouses who start mediation early on in their divorce tend to find that they get better results from the process. When spouses attend mediation sessions early, they can identify which issues are going to be contentious from the outset and can work to find mutually satisfactory resolutions before either spouse becomes too emotional or entrenched. If there is already animosity between the spouses when mediation starts, it can make it more difficult for the mediation process to move things forward in a productive way.