It depends on who garnished your wages to begin with. If it was the taxing authority, your state Dept. of Tax, or the IRS, yes the garnishment will include your tax refunds, if the Agent you're dealing with knows what he's doing. Only the government or a judicial court can take a tax refund away from you.
If it is a wage garnishment by any authority it will not effect the tax refund. That isn't to say tax authorities won't take the refund...they will (actually, well before they even bother coming after wages). But they do that under a process/law I believe normally called claim of right or offset, not the wage garnishment. Wage garnishment are directed at a specific employer and payroll.