There is a large amount of evidence that suggests Thomas Jefferson was indeed a freemason. First of all, Jefferson was a closer personal associate of many known Freemasons, including Benjamin Franklin and John Paul Jones. There is also some evidence to suggest that Jefferson attended Freemason meetings at a Masonic hall in Paris, France.
In my opinion and despite there being no evidence that he wore a Free Mason apron. The times that he lived in and the company that he kept as well as his own letters indicating that he knew the inner workings and rankings of the Free Masons in his circle of friends indicate to me that he was a well respected person in Mason society and would have been counted a member.