This handbook provides guidance for national programmes and organizations responsible for the care of older persons to develop, implement, monitor, and evaluate an mAgeing programme. The text messaging communication provided uses evidence-based behaviour change techniques to help older persons prevent and manage early declines in intrinsic capacity and functionalability. The mAgeing programme is based on WHO’s Integrated Care for Older People (ICOPE): Guidelines on community-level interventions to manage declines in intrinsic capacity which include interventions to prevent declines in intrinsic capacity and functional abilities in older people, namely: mobility loss, malnutrition, visual impairment and hearing loss; as well as cognitive impairments and depressive symptoms. The messages are designed to encourage participation in activities, and to prevent, reduce, or even partly reverse, significant losses in capacity. The content of the mAgeing programme will complement routine care offered by health care professionals by supporting self-care and self-management. All content in this handbook is based on the WHO ICOPE Guidelines and other relevant WHO recommendations. The ICOPE Guideline recommendations were reached by the consensus of a guideline development group, convened by WHO, which based its decisions on a summary of systematic reviews of the best quality evidence most relevant to community-level care for older people, as well as the most up-to-date research on the effectiveness of mHealth.