The objective of this research is to analyze the innovation strategy of sustainable family firms. An analysis of verbatim of managers in sustainable family firms showed that theyare constantly looking at a trade-off between stability and renewal. It highlights that the traditions act as safeguard against risky innovations. Afterward, a fine analysis ofstrategic choices in innovation made by a family firm was undertaken: it led to the specification of the concept of prudential innovation. This concept is then characterized throughseven features resulting from the commonly accepted characteristics of sustainable family firms.