In recent decades, life history theory (LHT) has provided an important theoretical framework for understanding human individual differences and their developmental processes. The conceptual complexity and multidisciplinary connections involved in the LH research, however, might appear daunting to psychologists whose research might otherwise benefit from the LH perspective. The main purpose of this review, therefore, is to introduce the evolutionary biological backgrounds and basic principles of LHT as well as their applications in developmental psychology. This review is organized into five parts, starting with an overview of key concepts in LHT, which clarifies the relationship among LH strategy, LH-related traits, and the fast–slow paradigm of LH variation. We proceed to review theoretical and empirical work related to four basic LH trade-offs, summarized by an integrated descriptive model of LH trade-offs that shape different LH strategies in humans. We then explain the effects of four aspects of environmental risks (morbidity-mortality threats, competition, resource scarcity, and unpredictability) on human LH strategy. This is followed by a discussion of LH calibration models in evolutionary developmental psychology that explicates the environmentally sensitive developmental processes that contribute to variation and plasticity in LH-related traits and ultimately human LH strategies. Finally, we highlight a few outstanding questions and future directions for LH research in psychology and conclude with why we think it is important that developmental psychology should embrace the LH approach.