Sometimes. The existing tile must be firmly bonded, clean, dry and suitable to support another layer. The installer should assess the surface and underlying floor before recommending an overlay. Loose tiles, cracks or signs of moisture need investigation first; covering them does not correct a failing base. The selected primer and setting materials must be approved for bonding to the existing surface.
Check the added floor height before choosing this approach. It can affect doors, thresholds and the relationship to nearby fixtures, while the extra weight must suit the supporting floor. If those details cannot be resolved, removing the old tile may be the better plan. Compare both options during design planning so the decision reflects the bathroom’s actual condition and finished levels, rather than just the appeal of avoiding demolition.