Is there a response to mazel tov?

Answer 1

The literal translation of Mazel Tov means Good Fortunes or Good Luck (i use "luck" for lack of a better word as Jews do not believe in luck). Though it is often used to say Congratulations.

So normally the correct answer would be to say "Thank You"

Answer 2

Three responses come to mind. 1). Most common, appropriate and useful in the US: "Thank you !" 2). In older Ashkenazic congregations: "ah SHAY-nem DAHNK !" ("A beautiful thank-you" in Yiddish.) 3). Most formal, least likely to be understood: "bah-RUCH tee-HYEH !" ("May it be a blessing" in Hebrew.)