This study investigated how a fear of falling affects perceptions and behavioral intentions toward age-friendly home modification (AFHM) in older parents and adult children by integrating the theory of planned behavior (TPB) to explain AFHM decision-making processes and the protection motivation theory to explain the impact of a fear of falling on AFHM intention. The target population comprised older parents (≥75 years old) and adult children (45–64 years old) in Busan, South Korea (N = 600). The participants completed a self-administered questionnaire in March 2022. Independentt-test and path model analyses were conducted to compare primary constructs between older parents and adult children and analyze the relationships among a fear of falling, TPB components, and AFHM intention. Results showed that both groups had positive attitudes toward AFHM. However, adult children showed significantly higher rates of having a fear of falling, lower perceived behavioral control, and higher AFHM intention than older parents. The proposed research models were partially supported in the older-parent group and fully supported in the adult-children group. Adult children play a critical role in AFHM, along with older adults who are directly involved in an aging society. AFHM-supporting programs, including monetary and human-force assistance, education, related public advertisements, and an active AFHM market, should be expanded.