Fractal structures represent a broad class of multiscale material structures that can find applications in stimuli-responsive materials. Design and optimization of the complex adaptive structures require understanding and tuning of multiscale transport properties of materials. Studying spatial and temporal diffusion further increases the complexity and introduces uncertainty in quantifying the model prediction. In this work, a series of 3D fractal structures with varying fractal dimensions were constructed using the diffusion-limited aggregation (DLA) algorithm. The fractal structures were 3D printed with a fused filament fabrication process (FFF), and transient heat-transfer properties were analyzed using thermal imaging. The experimental results were analyzed to obtain the time constants and characteristic length scales of diffusion as a function of the average fractal dimension.