This chapter analyzes how risk and ambiguity affect optimal investment in human and physical capital. Uncertainty is introduced in two ways: via the depreciation rate of human capital (reflecting skills obsolescence), and via the efficiency of its accumulation. When depreciation is uncertain, households tend to increase investment in human capital as a self-insurance strategy. However, when accumulation efficiency is uncertain, agents with CRRA utility and low risk aversion invest less, treating human capital as a risky asset rather than insurance. These results highlight distinct behaviors under different types of uncertainty.