Most Ginsu knives are labeled dishwasher safe by the manufacturer, but hand washing is still the better practice if you want the blades to stay sharp and looking good for the long term.
Ginsu is a knife brand (not a single product) that sells several product lines, including stainless steel and Japanese steel knife sets, and the specific care instructions can vary a bit by line and by individual product, so it's always worth checking the care label or manual that came with your particular set, or the product page on the retailer's site.
That said, here's the general guidance that applies to Ginsu knives and to quality kitchen knives in general:
- Dishwasher use is usually tolerated but not ideal. Repeated dishwasher cycles expose blades to heat, moisture, harsh detergent, and contact with other utensils, which can dull edges faster, cause pitting or discoloration, and degrade handle materials (especially wood or wood-composite handles) over time.
- Hand washing preserves sharpness and finish. Washing with warm water and mild dish soap, then drying immediately with a towel, is the recommended method to keep edges sharp longer and prevent spotting or rust, particularly on carbon-containing or high-carbon stainless blades.
- Handles matter. Knives with wooden or partial-tang wooden handles are more likely to warp, crack, or loosen at the rivets in a dishwasher, even if the blade itself is dishwasher-safe stainless steel.
- Serrated and specialty blades (like Ginsu's popular serrated steak knives) can also get duller faster from dishwasher jostling against other items.
Practical recommendation: if convenience matters more to you, dishwasher use should be fine occasionally for most Ginsu stainless pieces, but for the sharpest edge and longest-lasting knives, hand wash and dry them promptly instead of letting them sit wet in a dishwasher or sink.