Objective: Two studies examined the validity of using the Posttraumatic Growth Inventory (PTGI) to assess growth following the transition to grandparenthood as an aid for social workers seeking to promote strengths-based interventions for this population. Method: In Study 1 (n = 210 grandparent/offspring pairs), first-time grandparents' spontaneous answers to a qualitative open-ended question regarding changes following the birth of their first grandchild were compared to their responses to the PTGI. To corroborate these responses, the PTGI was also completed by the grandparent's offspring. Additionally, the study examined the applicability of the five-factor structure of the PTGI to the population of first-time grandparents. In Study 2 (n = 202 couples), grandparents' PTGI responses were compared with reports of their growth furnished by their spouses. Findings and conclusions: The PTGI can indeed be considered an effective instrument for measuring growth following the transition to grandparenthood and may therefore be used in designing strengths-based social work practices.