Metal foams or cellular structures like honeycombs, can also be evaluated according to mechanical, acoustic, thermal, and chemical resistance parameters in terms of functionality. However, it is vital to investigate the performance of these cellular structures' radiated emission (RE), which can be used as PCB heatsinks. In this study, the radiated emission (RE) performance of honeycomb-structured aluminum foam (or cellular) heatsinks (AFH), which can be considered as unidirectional regular foam, is examined in the frequency range of 1–10 GHz as a novelty. Also, the effect of four primary variables (the geometry of AFH, honeycomb hole direction, honeycomb cell size, and honeycomb cell wall thickness) on the RE performance of AFH is investigated. Unlike classical honeycomb production methods, the investment flask mold casting (loss wax) method is preferred due to the complex offset strip geometry of designed honeycombs. The original design offset hexagonal honeycomb structures were successfully produced using this investment casting method with additive manufacturing technologies from molten metal. While all simulations are carried out using CST Studio Suite, the RE performance of the proposed AFHs is measured in a standard 3 m fully anechoic chamber using a reference horn antenna and vector network analyzer (VNA). When the results are examined, the measured and simulated results agree with each other quietly. Regarding RE, structures with a CPI value of 14 are better at low frequencies, while structures with a CPI value of 3.5 are better at high frequencies. Secondly, the honeycomb cell thickness value does not significantly affect EMI performance. Lastly, although there is no significant difference in EMI in the low-frequency region, it is better to use a directional structure with vertical holes in the high-frequency region. As a result, in the design of AFH, the RE performances of the heatsinks and their thermal performance should be considered.