Broiler performance is dependent on immunocompetency and the ability to respond to environmental challenges. Incubation temperature, post-hatch transportation, and vaccination may impose stress upon the embryo and post-hatch chick and impact immune system development and lifetime performance of the bird. The objective of the first study was to evaluate incubation temperature and post-hatch transportation environment on response parameters indicative of early immunity in the neonatal chick. Cobb 500 eggs (n=5200) were incubated with combinations of eggshell temperatures common to commercial multi-stage incubators during early and late incubation: low (L): 36.7°C, standard (S): 37.5°C, and high (H): 39.0°C. After hatch, chicks were transported under one of two conditions: control (C: 34°C) or distressed (D: 40°C), yielding 8 experimental treatments: LH-C, LS-C, SH-C, SS-C, LH-D, LS-D, SH-D, and SS-D. The objective of the second study was to examine the effects of incubation temperature profiles on response to vaccination in Cobb 500 broilers (n=2000). Temperature treatments were the same as the first study, and embryos were administered vaccinations for Marek’s disease virus (MDV) at embryonic day (ED) 18, Newcastle disease virus (NDV) at hatch, the combination of MDV+NDV, or no vaccine (control). There were 16 resulting experimental groups: LH-Control, LH-MDV, LH-NDV, LH-MDV+NDV, LS-Control, LS-MDV, LS-NDV, LS-MDV+NDV, SH-Control, SH-MDV, SH-NDV, SH-MDV+NDV, SS-Control, SS-MDV, SS-NDV, and SS-MDV+NDV. Two and three way interactions (P<0.05) were observed for the parameters evaluated and are presented for both studies. These studies suggest an influence of incubation temperature and post-hatch stressors on chick development and early immune response parameters.