Wireless sensor networking technology has great potential to advance monitoring of animal environments. Recent applications are very limited due to a lack of understanding of the performance of wireless sensors in large-scale, concentrated, and confined animal feeding operations. Wireless sensor performance in poultry layer facilities was evaluated through empirical testing of path loss, which was measured as the received signal strength indicator value, using two commercial wireless sensor modules connected in a point-to-point configuration. Significant path loss was caused by free space, animal cages, animal presence, and concrete floor separations. The influence of each affecting factor was modeled based on the single slope derivation of the Friis free space path loss model. The transmission efficiency factor within a single aisleway was found to be 2.6. Fully stocked animal cages yielded an additional 22.5 and 24.9 dB path loss for one and two cages, respectively. Concrete floors separating levels of the test layer facility exhibited an additional path loss compared to the path loss at a similar distance when not separated by concrete. A two-dimensional path loss prediction model was developed based on the log of transmission distance, the number of aisle separations, a second-order aisle separation term, and an interaction term between separation distance and aisle separation. The model was able to predict 86% of the system variability and was able to produce an average error of -0.7 dB for all combined points. The model results are based on experimental measurements made versus a 1 mW transmission source and can thus be accurately scaled to predict the performance of higher or lower power transmission systems within a similarly designed poultry layer facility.