Walker distributed water bottles to volunteers and also helped remove graffiti from the sides of city buildings.
"You all have a reason to be kind. It is a common courtesy to be human. To help the best you can," he said in a video posted on Instagram.
He said that seeing the number of volunteers helping with cleaning was "inspiring" and "means a lot to this city".
San Antonio is one of several cities in the United States where protests took place over the death of Floyd, a black man who died last week in Minneapolis after Derek Chauvin, a white policeman, knelt on his neck for more than eight minutes.
Walker, in his second year at the University of Miami, told San Antonio Express News that "I am very proud to say that I am part of this community".
Walker later posted a statement on Twitter.
"During this protest, everyone is not seeing eye level, but we need to understand that we can only control what we can control," said part of the statement. "The best thing I've ever seen. At least here in San Antonio is that the COMMUNITY is coming together. People coming together and understanding the final issue. Black, white, Spanish, etc., all collectively as a group are coming together as one and moving accordingly. "
More life 🙏🏾 love you ….. pic.twitter.com/9e7e3n8ubO
– Lonnie Walker IV (@ lonniewalker_4) May 31, 2020