Answered by Sara, Hiring Expert at American Express, on Thursday, March 26, 2015
When you thank them for the interview, focus on the conversation you had to highlight your interest in the role and that you are an exceptional listener. This doesn't necessarily have to include a mention of your current employment, but it is likely that this topic will come up in your interview, so be honest.
Companies that have requested an interview will do their best to accommodate your availability, and a request for an after-hours interview may already be a signal that you are employed. Additionally, if your current place of employment is not listed on your resume, it is likely that your first interviewer will inquire into your employment. If they don't ask, you should feel comfortable to volunteer this information. Being forthcoming with this information is important in establishing trust between you and your future employer. Besides, having a job is a great thing!