The estranged former couple came to an agreement over twin sons Bob and Max, two, just days before the case was due back in front of a judge.
According to sources, the deal calls for joint legal and physical custody, although Mueller will get more time with the children than Sheen, reported TMZ.com.
The showbiz website reported the ex's lawyers went into the chambers of the Los Angeles judge on the case on Wednesday afternoon.
They brought the agreement, which apparently is only missing Sheen and Mueller's signatures.
The deal means the documents do not have to be filed with the court, meaning the details remain confidential.