McKellar and Mike Verta, a composer, filed for divorce last June, citing "irreconcilable differences." A judge made the divorce official this week, ruling that their pre-nup is still valid.
The Wonder Years alum initially asked for joint physical and legal custody of their 2-year-old son, and the custody and child support agreement is detailed in the sealed pre-nup.
The 38-year-old actress and math guru wed Verta in March 2009.
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