Ecotourism has been more and more promoted in many countries because it contributes to nature conservation, eco-education and income generation for local community. Vietnam has a great potential of ecotourism resources with a large system of national parks and protected areas, however the development of ecotourism in protected areas in Vietnam is not corrective to its potential. This paper analyzes tourists’ preferences for ecotourism services and biodiversity conservation in a protected area in Vietnam (the case in Phu My protected area) to support the decision–makers in ecotourism development process and nature conservation in the protected area in Vietnam. Choice experiments are employed to examine tourists’ interests in ecotourism services and estimate their willingness to pay for these ecotourism services as well as biodiversity conservation. The hypothetical ecotourism tours in the protected area were introduced with 5 attributes, including Crane-watching, craft-market visiting, fishing service, donation for biodiversity conservation and price of ecotourism tour. 199 tourists were interviewed directly and surveyed data were analyzed using Conditional Logit Model. Research results presents that tourists have an interest in the hypothetical ecotourism and prefer to enjoy all above ecotourism services. And tourist’s marginal willingness to pay for each ecotourism service is quite high. The study also reveals that tourists are willing to donate for biodiversity conservation activities in the protected area. Within the levels of donation suggested in the choice set, tourists prefer higher donation level.