I investigate the origins of social trust within Vietnam. Combining a unique contemporary survey of households with historic data on climate variation, I show that individuals who were heavily threatened by negative climate fluctuation exhibit more trust in neighbors and other people in close group. The evidence indicates that the effects of climate variation on social trust transmitted through strengthening the cooperation among village peasants in coping with risk and uncertainty. The results also indicate that households with higher proportion of agricultural incomes tend to rely more on village members in the case of emergency. However, the increased village relationship does not erode family ties.