Harry, who is currently on tour in the USA chatted to the Californian champion, who took home four gold medals during London 2012. Dressed in a smart navy blue suit and tie Harry asked spoke to Missy about her glittering career before joining the crowd in singing Happy Birthday.
"And the perfect way to end my 18th birthday!?" tweeted the happy Olympian. "Meeting Prince Harry! It was a honor meeting him and I had a blast as always."
Earlier in the day Harry visited the Walter Reed National Military Center, where he spent time meeting injured soldiers. The Prince was also given a tour of the prosthetics and rehabilitation centre for service personnel.
On Saturday, Harry is in Colorado Springs to watch the opening ceremony of the Warrior Games where injured servicemen and women will compete.
It is the first time that Britain will compete in the Paralympic-style competition. Prince Harry, who met competitors last year, is known to be a big fan of the event and its cause.
Harry then has a series of engagements lined up across New Jersey, Connecticut and New York before heading back to the UK on Thursday.