Melon (Cucumis melo L.; Cucurbitaceae) is one of the 10 most-consumed fruits in the world. The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most important pests in melon crops worldwide. Conventional sampling plans are the starting point to establish decisionmaking systems for integrated pest management (IPM) programs. The purpose of this study was to determine a conventional sampling plan for B. tabaci in melon crops with plants at the vegetative, flowering, and fruiting stages. The best sampling units for B. tabaci were the 5th and 6th most apical leaves of the plant vine. The best sampling technique was direct counting of adult whiteflies. The most appropriate frequency distribution to describe B. tabaci densities in melon fields was the negative binomial. Whiteflies on melon fields with plants at different phenological stages showed a common aggregation parameter (Kcommon = 0.9134). The optimal number of samples from the sampling plan was 72 samples per field with a maximum error of 15% in population determination. The sampling plan determined by this study can be used by farmers because it is a low-cost (US$5.27 per sampling), fast (39 minutes per sampling) and feasible (15% maximum evaluation error). The same sampling plan can be used with melon plants at the vegetative, flowering, and fruiting stages.