This study investigates returns of scale, estimates technical efficiency, and identifies the determinant factors of the efficiency of small-scale cassava farming in Vientiane and Savannakhet provinces, Lao PDR. Cross-sectional data on inputs, output, and farming characteristics from 193 cassava farmers were collected for this study. The maximum likelihood method is employed to estimate parameters, elasticity, and inefficiency scores using the stochastic frontier production function model. This study found that the elasticity of the mean value of cassava output is estimated to be an increasing function of farm size, labor cost, and seed cost in Vientiane and Savannakhet. Increasing returns to scale was found for smallholder cassava farming in Savannakhet. The estimated mean score of technical efficiency are 72 percent and 75 percent for Vientiane and Savannakhet, respectively. The determinants of technical efficiency in Vientiane showed that planting cassava with good land preparation, suitable time period for plantation, and young farmers play a key role in the improvement of technical efficiency for cassava farming.