The couple, who announced their engagement Monday, will spend the morning at the event, hosted by the Terrence Higgins Trust.
Harry and Markle will then meet head teachers at a nearby school, Kensington Palace confirmed.
At Nottingham Academy, the couple will watch a “hip hopera” and say hello to some students.
Word obviously got out about Prince Harry and his wife-to-be being in town, with well-wishers gathering outside the National Justice Museum in droves with the hope of catching a glimpse of the couple.
As the couple met one person in particular, Harry was asked, “how does it feel being a ginger with Meghan?” to which he replied, “It’s great, isn’t it?”
Their appearance comes after it was revealed on Tuesday that the pair will marry at St. George’s Chapel, Windsor Castle, next May.
Kensington Palace announced the news just a day after it was revealed that Harry had popped the question.
Harry’s communications secretary Jason Knauf described Windsor as a “very special place” for the couple, saying they had spent time there together since meeting in July 2016.
He said in a statement: “The couple of course want the day to be a special, celebratory moment for their friends and family. They also want the day to be shaped so as to allow members of the public to feel part of the celebrations too and are currently working through ideas for how this might be achieved.”
“This wedding, like all weddings, will be a moment of fun and joy that will reflect the characters of the Bride and Groom.”