Being able to obtain a clear picture of staff’s mental health (MH) status is fundamental to deciding proper MH care approach or policy. This paper shares the experience induced results gained from a MH survey on librarians across Vietnam. They include the selection of MH assessment tools, survey design and administration considerations to ensure quality, validity and comprehensiveness for the data collected. The most significant experience is about the choice of the WHO-5 Wellbeing Index over other MH assessment tools, the combined use of this tool together with two other validated scales, namely the LOT-R 1994, and the Strahan-Gerbasi X1 scale to assess mental wellbeing of the subjects while judging its reliability through how it correlates with general optimism levels, and controlling for socially desirable responding. These arrangements are necessary given the stigma-attached nature of MH and the typical resultant hindrances to MH research. It is hoped that the experience shared will be drawn on or further developed in other similar research. The strongly-established research design and considerations will increase the chance of a MH-driven research to become successful, bringing reliable evidence to any MH care implementation.