Dress Code for Portugal

Wear what makes your feet happy, that's all that matters. I've seen people all over Europe wearing athletic shoes, tourists and locals alike.

You will most likely stand out as a "tourist", regardless of your shoes.

Wear comfy shoes

The big thing with any shoes you wear is making certain they have thick soles with ability to grip the cobblestones. You will be walking on cobblestones 95%+ of the time and they aren't always even. And, if it rains, be even more cautious as the cobblestones become quite slick when wet. That said - they are also lovely and add a lot of charm and character.
And, yes, lots of people wear athletic shoes.

I second all of the above replies. I wore my bright blue gym shoes and stood out, but my feet were comfortable (and yes, the streets are slippery when wet). I did see a lot of closed-toe leather sandals, sport shoes, athletic shoes, and quite a few Stan Smiths. Have a great time and don't worry about what shoes you wear.

I've been to Europe several times, but I was fretting what to wear to Portugal next week. All the online guides said no sneakers of any kind, no t-shirts, etc. Then, I went to Google Earth and guess what? Everyone in Lisbon was wearing athletic shoes!!!!! Sure, they could have been tourists, but at least you won't stand out.
I'm blond with green eyes, so I know I won't be mistaken for a local. For me, the key is to strike a happy medium: lightweight casual polo-style shirts, jeans in dark colors, and grey slip-ons.

Wear what you like and feel comfy in. Happy travels!

I'm in Lisbon right now. I couldn't answer your question about what the locals wear if I had to because I'm not spending my time looking at their feet. And neither will they. They'll know you're a tourist from all the other signs they're used to seeing for decades. Shoes won't make a difference. From what I have paid attention to about how the locals dress, they all look like Americans. Which would explain why many of their clothing stores in the malls are American companies. They all dress to be comfortable in their city. We should too.

Casual dress and comfortable shoes for locals and tourist. Young local ladies were into very short lower body wear, was it a skort, skirt or shorts?