Text alignment in DataGrid

You need set DataGridCell style

    <DataGrid>
        <DataGrid.Columns>
            <DataGridTextColumn>
                <DataGridTextColumn.ElementStyle>
                    <Style TargetType="TextBlock">
                        <Setter Property="HorizontalAlignment" Value="Center" />
                    </Style>
                </DataGridTextColumn.ElementStyle>
            </DataGridTextColumn>
        </DataGrid.Columns>
    </DataGrid>