This paper examines the effect of AIDS-related mortality of the prime-age adult population on marriage behavior among women in Malawi. A rise in prime-age adult mortality increases risks associated with the search for a marriage partner in the marriage market. A possible behavioral change in the marriage market in response to an increase in prime-age adult mortality is for marriage to occur earlier to avoid women’s exposure to HIV/AIDS risks under the condition that the risks are higher during singlehood. We test this hypothesis using micro data from Malawi, where prime-age adult mortality has drastically increased. In the analysis, we estimate prime-age adult mortality that sample women have observed during the adolescent period by utilizing retrospective information on the death of their siblings. Empirical analysis shows that excess prime-age adult mortality observed in the local marriage market (district) lowers the marriage age for females and reduces their premarital sexual activities. Since a lower age for first marriage implies less schooling completed, we expect that the average schooling achievement among women would decline. This behavioral change also implies a longer reproduction period during their marriage, which may lead to a higher fertility rate. However, the second implication should be discounted if the reduction of sexual activities also applies to the married population. Lower schooling attainment among women has further implications on human capital formation in the next generation.