The government aims to accede to the 1980 Hague Convention on the Civil Aspects of International Child Abduction on April 1.
Japan had been accused by the United States and European countries of being a "safe haven" for international child abductions.
The treaty, which currently has 89 signatories, sets out rules and procedures for the prompt return to the country of habitual residence of children under 16 taken to another country, if requested by the other parent.
The convention will enter into force in a state acceding to it on the first day of the third calendar month after the instrument of accession is deposited with the Dutch Foreign Ministry.
The Diet approved the country's accession to the treaty in May and enacted a law in June stipulating domestic implementation procedures for the Hague treaty.
Under the legislation, a central authority will be set up in the Foreign Ministry to locate children who have been taken away and encourage the people involved to settle the dispute through consultations.
If the consultations fail, family courts in Tokyo and Osaka will decide on the child's treatment. The legislation also allows a parent to refuse to return a child if abuse or domestic violence is feared.
The central authority will be staffed with lawyers, experts on domestic violence and child psychology counselors.
At the family courts in Tokyo and Osaka, judges have been trained on the Hague convention. The Foreign Ministry and the family courts plan to open a website to explain about the procedures to settle disputes under the pact.
The government plans to join the international treaty for settling cross-border child custody disputes in April after submitting necessary documents in January to the Dutch Foreign Ministry, which handles matters on the pact, a government source said Tuesday.