Since the late 1990s, various development efforts and research initiatives have been conducted by national research institutions and international development agencies for the economic development of the Northwest Highlands of Vietnam. A shift towards a research for development approach, which targets the immediate use of research outputs for development purposes, became apparent in the late 2000s. These agricultural research for development (AR4D) projects have adopted participatory processes in an attempt to better link the research with development. It is important to understand the contribution of these AR4D projects to rural development, not only in terms of knowing the extent of the impacts and their sustainability but also for informing appropriate agricultural policies and research for development strategies in the future.Despite the importance of knowing the impacts of AR4D, the impact assessment of agricultural research initiatives in the Northwest Highlands remains problematic in regard to both the objectives and methods. This study developed a holistic impact assessment framework for the Highlands and tested the proposed framework in order to validate its appropriateness and gain insights into how AR4D underpinned by participatory processes can contribute to better changes in people's lives. The results of the application of this framework would also help to inform future development policies and effective AR4D interventions with a particular focus on a highly culturally diverse region.To achieve the overall objective, this study employed mixed methods largely based on qualitative data collection methods in combination with documentary research. The documentary research included a review of the literature on development theories and practices related to the impact assessment of AR4D projects. It also included an examination of secondary sources on the impact assessment approaches in agricultural research projects implemented by active research institutions and development agencies in the Northwest Highlands. The primary data was collected by primarily using qualitative methods such as focus group discussions (FGDs) with farmers, semi-structured interviews with farmers, and in-depth interviews with key informants including local leaders, agricultural extension staff and agricultural researchers who were actively involved in research projects in the Highlands. This was complemented by a limited amount of quantitative data derived from the interviews. The fieldwork was conducted in two districts of Son La province, covering the implementation sites of three agricultural research projects. The purposive sampling method was used for the selection of participants of both the FGDs and in-depth interviews. Three field trips to Son La were made, in December 2012, September 2013 and July 2014.The initial findings were reported back to the participants in order to elicit their feedback and validate the data. All the gathered primary data and information was recorded, reviewed and translated into English...