The present investigation explored (1) fathers' contributions to children's theory of mind (ToM) development, (2) the similarity between maternal and paternal mind-mindedness (MM) in relation to children's ToM, and (3) the relative predictive strength of two concurrently administered measures of MM (an online and an interview assessment) in relation to children's ToM. Thirty-nine fathers, mothers, and their four-year-olds participated. Paternal MM was positively correlated with children's ToM performance. In addition, the two groups of parents performed similarly on both measures of MM. The findings also suggest that mothers and fathers who scored higher on the MM interview were more attuned to their children's mental processes during the online interaction measure of MM. The online measure of MM was found to mediate the relationship between the interview measure of MM and children's ToM for the maternal-child data only. (Contains 5 tables and 2 figures.)