As it has been seen in previous chapters, delay differential equations exhibit much more complicated dynamics than ordinary differential equations since a time-delay could cause a stable equilibrium to become unstable and cause the populations to fluctuate. In this chapter, we study delay differential equations of prey-predator systems with Allee effect. The dynamical relationship between the prey and their predators has long been and will continue to be one of the dominant themes in ecology due to its universal existence and importance (see, e.g., Kot, Elements of mathematical ecology. Cambridge University Press, Cambridge, 2001; Li and Liu, Adv Differ Equ 2016(1):42, 2016; Liu and Tan, Chaos, Solitons & Fractals 34(2):454–464, 2007; Murray, Mathematical biology II. Springer, 2003). This relationship/interaction between two or more species has been essential in theoretical ecology since the famous Lotka-Volterra equations (Lotka, Elements of physical biology. Williams and Wilkins, Baltimore, 1925; Volterra, Nature 118(1926):558–560), which are a system of first-order, nonlinear differential equations that describe the dynamics and interactions between two or more species of biological systems. Of course, the qualitative properties of a prey-predator system, such as stability of the steady states, bifurcation analysis, and oscillation of the solutions, usually depend on the system parameters; see Kuang (Delay differential equations with applications in population dynamics. Academic, 1993).