<Window ...
xmlns:local="clr-namespace:MyNamespace"
>
<TabControl>
<TabItem Header="FirstTab">
<local:MyFirstTabUserControl/>
</TabItem>
<TabItem Header="SecondTab">
<local:MySecondTabUserControl/>
</TabItem>
<TabItem Header="ThirdTab">
<local:MyThirdTabUserControl/>
</TabItem>
</TabControl>
</Window>
TabUserControl UserControl, TabItem .