The common laboratory zebrafish can regenerate functional cardiac muscle after cataclysmic damage or loss, by activating programs that direct the division of spared cardiomyocytes. Heart regeneration is not a linear series of molecular steps and synchronized cellular progressions, but rather an imperfect, relentless process that proceeds in an advantaged competition with scarring until recovery of the lost heart function. In this review, we summarize recent advances in our understanding of signaling events that have formative roles in injury-induced cardiomyocyte proliferation in zebrafish, and we forecast advances in the field that are needed to decipher heart regeneration.